Barplot: Why do i get a variable spacing between bars in ggplot2 for identical script?

Question

I'm running into something bizarre with ggplot2. I have a loop script that produces barplots and save each one of them as a tiff file. I don't want any spacing between the bars, and I think I have the script written correctly to do just that, but some of my graphs show hair lines between bars and some don't. Because it is a loop, the script and data structure is exactly the same for both of them. Here is a reproducible example:

 require(gridExtra); require(ggplot2); require(grid)
 prod.data1 = structure(list(date.time = structure(c(1465362000, 1465365600, 
    1465369200, 1465372800, 1465376400, 1465380000, 1465383600, 1465387200, 
    1465390800, 1465394400, 1465398000, 1465401600, 1465405200, 1465408800, 
    1465412400, 1465416000, 1465419600, 1465423200, 1465426800, 1465430400, 
    1465434000, 1465437600, 1465441200, 1465444800, 1465448400, 1465452000, 
    1465455600, 1465459200, 1465462800, 1465466400, 1465470000, 1465473600, 
    1465477200, 1465480800, 1465484400, 1465488000, 1465491600, 1465495200, 
    1465498800, 1465502400, 1465506000, 1465509600, 1465513200, 1465516800, 
    1465520400, 1465524000, 1465527600, 1465531200, 1465534800, 1465538400, 
    1465542000, 1465545600, 1465549200, 1465552800, 1465556400, 1465560000, 
    1465563600, 1465567200, 1465570800, 1465574400, 1465578000, 1465581600, 
    1465585200, 1465588800, 1465592400, 1465596000, 1465599600, 1465603200, 
    1465606800, 1465610400, 1465614000, 1465617600, 1465621200, 1465624800, 
    1465628400, 1465632000, 1465635600, 1465639200, 1465642800, 1465646400, 
    1465650000, 1465653600, 1465657200, 1465660800, 1465664400, 1465668000, 
    1465671600, 1465675200, 1465678800, 1465682400, 1465686000, 1465689600, 
    1465693200, 1465696800, 1465700400, 1465704000, 1465707600, 1465711200, 
    1465714800, 1465718400, 1465722000, 1465725600, 1465729200, 1465732800, 
    1465736400, 1465740000, 1465743600, 1465747200, 1465750800, 1465754400, 
    1465758000, 1465761600, 1465765200, 1465768800, 1465772400, 1465776000, 
    1465779600, 1465783200, 1465786800, 1465790400, 1465794000, 1465797600, 
    1465801200, 1465804800, 1465808400, 1465812000, 1465815600, 1465819200, 
    1465822800, 1465826400, 1465830000, 1465833600, 1465837200, 1465840800, 
    1465844400, 1465848000, 1465851600, 1465855200, 1465858800, 1465862400, 
    1465866000, 1465869600, 1465873200, 1465876800, 1465880400, 1465884000, 
    1465887600, 1465891200, 1465894800, 1465898400, 1465902000, 1465905600, 
    1465909200, 1465912800, 1465916400, 1465920000, 1465923600, 1465927200, 
    1465930800, 1465934400, 1465938000, 1465941600, 1465945200, 1465948800, 
    1465952400, 1465956000, 1465959600, 1465963200, 1465966800, 1465970400, 
    1465974000, 1465977600, 1465981200, 1465984800, 1465988400, 1465992000, 
    1465995600, 1465999200, 1466002800, 1466006400, 1466010000, 1466013600, 
    1466017200, 1466020800, 1466024400, 1466028000, 1466031600, 1466035200, 
    1466038800, 1466042400, 1466046000, 1466049600, 1466053200, 1466056800, 
    1466060400, 1466064000, 1466067600, 1466071200, 1466074800, 1466078400, 
    1466082000, 1466085600, 1466089200, 1466092800, 1466096400, 1466100000, 
    1466103600, 1466107200, 1466110800, 1466114400, 1466118000, 1466121600, 
    1466125200, 1466128800, 1466132400, 1466136000), class = c("POSIXct", 
    "POSIXt")), production = c(5.9, 5.9, 5.9, 5.9, 5.9, 5.9, 9.9, 
    9.9, 9.9, 9.9, 9.9, 9.9, 9.9, 9.9, 9.9, 13.4, 13.4, 13.4, 13.4, 
    13.4, 13.4, 9.9, 5.9, 5.9, 5.9, 5.9, 5.9, 5.9, 5.9, 5.9, 9.9, 
    9.9, 9.9, 9.9, 9.9, 9.9, 9.9, 9.9, 9.9, 13.4, 13.4, 13.4, 13.4, 
    13.4, 13.4, 9.9, 5.9, 5.9, 5.9, 5.9, 5.9, 5.9, 5.9, 5.9, 9.9, 
    9.9, 9.9, 9.9, 9.9, 9.9, 9.9, 9.9, 9.9, 13.4, 13.4, 13.4, 13.4, 
    13.4, 13.4, 9.9, 5.9, 5.9, 5.9, 5.9, 5.9, 5.9, 5.9, 5.9, 9.9, 
    9.9, 9.9, 9.9, 9.9, 9.9, 9.9, 9.9, 9.9, 13.4, 13.4, 13.4, 13.4, 
    13.4, 13.4, 9.9, 5.9, 5.9, 3.1, 3.1, 3.1, 3.1, 3.1, 3.1, 7.1, 
    7.1, 7.1, 7.1, 7.1, 7.1, 7.1, 7.1, 7.1, 7.1, 7.1, 7.1, 7.1, 7.1, 
    7.1, 3.1, 3.1, 3.1, 3.1, 3.1, 3.1, 3.1, 3.1, 3.1, 7.1, 7.1, 7.1, 
    7.1, 7.1, 7.1, 7.1, 7.1, 7.1, 7.1, 7.1, 7.1, 7.1, 7.1, 7.1, 3.1, 
    3.1, 3.1, 3.1, 3.1, 3.1, 3.1, 3.1, 3.1, 7.1, 7.1, 7.1, 7.1, 7.1, 
    7.1, 7.1, 7.1, 7.1, 7.1, 7.1, 7.1, 7.1, 7.1, 7.1, 3.1, 3.1, 3.1, 
    3.1, 3.1, 3.1, 3.1, 3.1, 3.1, 7.1, 7.1, 7.1, 7.1, 7.1, 7.1, 7.1, 
    7.1, 7.1, 7.1, 7.1, 7.1, 7.1, 7.1, 7.1, 3.1, 3.1, 3.1, 3.1, 3.1, 
    3.1, 3.1, 3.1, 3.1, 7.1, 7.1, 7.1, 7.1, 7.1, 7.1, 7.1, 7.1, 7.1, 
    7.1, 7.1, 7.1, 7.1, 7.1, 7.1, 3.1, 3.1, 3.1), ID = structure(c(15L, 
    15L, 15L, 15L, 15L, 15L, 15L, 15L, 15L, 15L, 15L, 15L, 15L, 15L, 
    15L, 15L, 15L, 15L, 15L, 15L, 15L, 15L, 15L, 15L, 15L, 15L, 15L, 
    15L, 15L, 15L, 15L, 15L, 15L, 15L, 15L, 15L, 15L, 15L, 15L, 15L, 
    15L, 15L, 15L, 15L, 15L, 15L, 15L, 15L, 15L, 15L, 15L, 15L, 15L, 
    15L, 15L, 15L, 15L, 15L, 15L, 15L, 15L, 15L, 15L, 15L, 15L, 15L, 
    15L, 15L, 15L, 15L, 15L, 15L, 15L, 15L, 15L, 15L, 15L, 15L, 15L, 
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    15L, 15L, 15L, 15L, 15L, 15L, 15L, 15L, 15L, 15L, 15L, 15L, 15L, 
    15L, 15L, 15L, 15L, 15L, 15L, 15L, 15L, 15L, 15L, 15L, 15L, 15L, 
    15L, 15L, 15L, 15L, 15L, 15L, 15L, 15L, 15L, 15L, 15L, 15L, 15L, 
    15L, 15L, 15L, 15L, 15L, 15L, 15L, 15L, 15L, 15L, 15L, 15L, 15L, 
    15L, 15L, 15L, 15L, 15L, 15L, 15L, 15L, 15L, 15L, 15L, 15L, 15L, 
    15L, 15L, 15L, 15L, 15L, 15L, 15L, 15L, 15L, 15L, 15L, 15L, 15L, 
    15L, 15L, 15L, 15L, 15L, 15L, 15L, 15L, 15L, 15L, 15L, 15L, 15L, 
    15L, 15L, 15L, 15L, 15L, 15L, 15L, 15L, 15L, 15L, 15L, 15L, 15L, 
    15L, 15L, 15L, 15L, 15L, 15L, 15L, 15L, 15L, 15L, 15L, 15L, 15L, 
    15L, 15L, 15L, 15L, 15L, 15L, 15L), .Label = c("A", "B", "C","D", 
    "E", "F", "G", "H", "I", "J", "K", "L", "M", "N", "O", "P"), 
    class = "factor"), ILP = c(10.72, 
    8.66, 7.75, 7.25, 7.91, 9.12, 10.33, 12.93, 15.7, 15.72, 16.7, 
    15.34, 14.6, 14.34, 13.09, 11.52, 12.08, 13.29, 14.56, 13.74, 
    15.46, 15.37, 12.49, 11.11, 7.78, 5.92, 5.92, 5.91, 6.11, 7.01, 
    10.05, 10.49, 11.43, 11.45, 12.21, 12.79, 12.09, 11.94, 11.99, 
    10.87, 11.31, 12.08, 13.33, 13.31, 14.23, 13.01, 10.84, 10.07, 
    7.08, 5.04, 5.01, 5.06, 5.22, 6, 9.92, 10.74, 12.53, 12.43, 13.34, 
    13.24, 13.52, 12.95, 13.86, 13.09, 13.79, 12.44, 14.14, 14.05, 
    14.36, 14.45, 11.66, 10.4, 11.3366666666667, 11.3366666666667, 
    11.3366666666667, 11.3366666666667, 11.3366666666667, 11.3366666666667, 
    11.3366666666667, 11.3366666666667, 11.3366666666667, 11.3366666666667, 
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    11.3366666666667, 11.3366666666667, 11.3366666666667, 11.3366666666667, 
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    11.3366666666667, 11.3366666666667, 11.3366666666667, 11.3366666666667, 
    11.3366666666667, 11.3366666666667, 11.3366666666667, 11.3366666666667, 
    11.3366666666667, 11.3366666666667, 11.3366666666667, 11.3366666666667, 
    11.3366666666667, 11.3366666666667, 11.3366666666667, 11.3366666666667, 
    11.3366666666667, 11.3366666666667, 11.3366666666667, 11.3366666666667, 
    11.3366666666667, 11.3366666666667, 11.3366666666667, 11.3366666666667, 
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    11.3366666666667, 11.3366666666667, 11.3366666666667, 11.3366666666667, 
    11.3366666666667, 11.3366666666667, 11.3366666666667, 11.3366666666667, 
    11.3366666666667, 11.3366666666667, 11.3366666666667, 11.3366666666667, 
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    11.3366666666667, 11.3366666666667, 11.3366666666667, 11.3366666666667, 
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    11.3366666666667, 11.3366666666667, 11.3366666666667, 11.3366666666667, 
    11.3366666666667, 11.3366666666667), Class = structure(c(2L, 2L, 
    2L, 2L, 2L, 2L, 2L, 2L, 4L, 4L, 4L, 3L, 3L, 3L, 3L, 2L, 2L, 3L, 
    3L, 3L, 4L, 3L, 2L, 2L, 2L, 2L, 2L, 2L, 2L, 2L, 2L, 2L, 3L, 3L, 
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    4L, 4L, 4L, 4L, 2L, 2L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 
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    1L, 1L, 1L, 1L, 1L, 1L), .Label = c("NA", "Low", "Medium", 
    "High"), class = "factor")), .Names = c("date.time", "production", 
    "ID", "ILP", "Class"), row.names = 3025:3240, class = "data.frame")

prod.data2 = structure(list(date.time = structure(c(1465362000, 1465365600, 
1465369200, 1465372800, 1465376400, 1465380000, 1465383600, 1465387200, 
1465390800, 1465394400, 1465398000, 1465401600, 1465405200, 1465408800, 
1465412400, 1465416000, 1465419600, 1465423200, 1465426800, 1465430400, 
1465434000, 1465437600, 1465441200, 1465444800, 1465448400, 1465452000, 
1465455600, 1465459200, 1465462800, 1465466400, 1465470000, 1465473600, 
1465477200, 1465480800, 1465484400, 1465488000, 1465491600, 1465495200, 
1465498800, 1465502400, 1465506000, 1465509600, 1465513200, 1465516800, 
1465520400, 1465524000, 1465527600, 1465531200, 1465534800, 1465538400, 
1465542000, 1465545600, 1465549200, 1465552800, 1465556400, 1465560000, 
1465563600, 1465567200, 1465570800, 1465574400, 1465578000, 1465581600, 
1465585200, 1465588800, 1465592400, 1465596000, 1465599600, 1465603200, 
1465606800, 1465610400, 1465614000, 1465617600, 1465621200, 1465624800, 
1465628400, 1465632000, 1465635600, 1465639200, 1465642800, 1465646400, 
1465650000, 1465653600, 1465657200, 1465660800, 1465664400, 1465668000, 
1465671600, 1465675200, 1465678800, 1465682400, 1465686000, 1465689600, 
1465693200, 1465696800, 1465700400, 1465704000, 1465707600, 1465711200, 
1465714800, 1465718400, 1465722000, 1465725600, 1465729200, 1465732800, 
1465736400, 1465740000, 1465743600, 1465747200, 1465750800, 1465754400, 
1465758000, 1465761600, 1465765200, 1465768800, 1465772400, 1465776000, 
1465779600, 1465783200, 1465786800, 1465790400, 1465794000, 1465797600, 
1465801200, 1465804800, 1465808400, 1465812000, 1465815600, 1465819200, 
1465822800, 1465826400, 1465830000, 1465833600, 1465837200, 1465840800, 
1465844400, 1465848000, 1465851600, 1465855200, 1465858800, 1465862400, 
1465866000, 1465869600, 1465873200, 1465876800, 1465880400, 1465884000, 
1465887600, 1465891200, 1465894800, 1465898400, 1465902000, 1465905600, 
1465909200, 1465912800, 1465916400, 1465920000, 1465923600, 1465927200, 
1465930800, 1465934400, 1465938000, 1465941600, 1465945200, 1465948800, 
1465952400, 1465956000, 1465959600, 1465963200, 1465966800, 1465970400, 
1465974000, 1465977600, 1465981200, 1465984800, 1465988400, 1465992000, 
1465995600, 1465999200, 1466002800, 1466006400, 1466010000, 1466013600, 
1466017200, 1466020800, 1466024400, 1466028000, 1466031600, 1466035200, 
1466038800, 1466042400, 1466046000, 1466049600, 1466053200, 1466056800, 
1466060400, 1466064000, 1466067600, 1466071200, 1466074800, 1466078400, 
1466082000, 1466085600, 1466089200, 1466092800, 1466096400, 1466100000, 
1466103600, 1466107200, 1466110800, 1466114400, 1466118000, 1466121600, 
1466125200, 1466128800, 1466132400, 1466136000), class = c("POSIXct", 
"POSIXt")), production = c(17.9, 17.9, 17.9, 17.9, 17.9, 17.9, 
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17.9, 17.9, 17.9, 17.9, 17.9, 17.9, 17.9, 17.9, 17.9, 17.9, 17.9, 
59.4, 64.7, 73.7, 56.2, 32.2, 23.2, 17.9, 17.9, 17.9, 17.9, 17.9, 
17.9, 17.9), ID = structure(c(4L, 4L, 4L, 4L, 4L, 4L, 4L, 4L, 
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4L, 4L, 4L, 4L, 4L, 4L, 4L, 4L, 4L, 4L, 4L, 4L, 4L, 4L, 4L, 4L, 
4L, 4L, 4L, 4L, 4L, 4L, 4L, 4L, 4L, 4L, 4L, 4L, 4L, 4L, 4L, 4L, 
4L, 4L, 4L, 4L, 4L, 4L, 4L, 4L, 4L, 4L, 4L, 4L, 4L, 4L, 4L, 4L, 
4L, 4L, 4L, 4L, 4L, 4L, 4L, 4L, 4L, 4L, 4L, 4L, 4L, 4L, 4L, 4L
), .Label = c("A", "B", "C","D", "E", "F", "G", "H", "I", "J", 
"K", "L", "M", "N", "O", "P"), class = "factor"), ILP = c(19.8, 19.06, 14.88, 
13.28, 12.3, 13.2, 18.95, 21.19, 21.37, 25, 25.75, 25.57, 25.19, 
23.31, 23.4, 22.69, 25.37, 24.96, 22.53, 20.54, 22.21, 20.26, 
18.94, 16.29, 16.89, 14.21, 12.72, 11.18, 10.26, 11.69, 15.95, 
18.23, 19.11, 19.78, 20.35, 20.15, 21.17, 22.45, 23.7, 24.04, 
25.58, 25.35, 21.73, 19.81, 20.77, 21.05, 20.58, 17.48, 16.09, 
14.15, 11.13, 10.14, 9.76, 11.16, 14.29, 18.79, 18.99, 19.45, 
19.52, 19.45, 20.38, 20.15, 21.52, 20.2, 20.96, 20.56, 18.42, 
17.33, 17.31, 16.95, 18.92, 15.59, 18.9094444444444, 18.9094444444444, 
18.9094444444444, 18.9094444444444, 18.9094444444444, 18.9094444444444, 
18.9094444444444, 18.9094444444444, 18.9094444444444, 18.9094444444444, 
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18.9094444444444, 18.9094444444444, 18.9094444444444, 18.9094444444444, 
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18.9094444444444, 18.9094444444444, 18.9094444444444, 18.9094444444444, 
18.9094444444444, 18.9094444444444, 18.9094444444444, 18.9094444444444, 
18.9094444444444, 18.9094444444444, 18.9094444444444, 18.9094444444444, 
18.9094444444444, 18.9094444444444, 18.9094444444444, 18.9094444444444, 
18.9094444444444, 18.9094444444444, 18.9094444444444, 18.9094444444444, 
18.9094444444444, 18.9094444444444, 18.9094444444444, 18.9094444444444, 
18.9094444444444, 18.9094444444444, 18.9094444444444, 18.9094444444444, 
18.9094444444444, 18.9094444444444, 18.9094444444444, 18.9094444444444, 
18.9094444444444, 18.9094444444444, 18.9094444444444, 18.9094444444444, 
18.9094444444444, 18.9094444444444, 18.9094444444444, 18.9094444444444, 
18.9094444444444, 18.9094444444444, 18.9094444444444, 18.9094444444444, 
18.9094444444444, 18.9094444444444, 18.9094444444444, 18.9094444444444, 
18.9094444444444, 18.9094444444444, 18.9094444444444, 18.9094444444444, 
18.9094444444444, 18.9094444444444, 18.9094444444444, 18.9094444444444, 
18.9094444444444, 18.9094444444444, 18.9094444444444, 18.9094444444444, 
18.9094444444444, 18.9094444444444, 18.9094444444444, 18.9094444444444, 
18.9094444444444, 18.9094444444444, 18.9094444444444, 18.9094444444444, 
18.9094444444444, 18.9094444444444, 18.9094444444444, 18.9094444444444, 
18.9094444444444, 18.9094444444444, 18.9094444444444, 18.9094444444444, 
18.9094444444444, 18.9094444444444, 18.9094444444444, 18.9094444444444, 
18.9094444444444, 18.9094444444444, 18.9094444444444, 18.9094444444444, 
18.9094444444444, 18.9094444444444, 18.9094444444444, 18.9094444444444, 
18.9094444444444, 18.9094444444444, 18.9094444444444, 18.9094444444444, 
18.9094444444444, 18.9094444444444, 18.9094444444444, 18.9094444444444, 
18.9094444444444, 18.9094444444444, 18.9094444444444, 18.9094444444444, 
18.9094444444444, 18.9094444444444, 18.9094444444444, 18.9094444444444, 
18.9094444444444, 18.9094444444444), Class = structure(c(2L, 2L, 
2L, 2L, 2L, 2L, 2L, 2L, 3L, 3L, 4L, 4L, 4L, 3L, 3L, 3L, 4L, 3L, 
3L, 2L, 3L, 2L, 2L, 2L, 2L, 2L, 2L, 2L, 2L, 2L, 2L, 2L, 2L, 2L, 
3L, 3L, 3L, 3L, 4L, 4L, 4L, 4L, 3L, 2L, 3L, 3L, 3L, 2L, 2L, 2L, 
2L, 2L, 2L, 2L, 2L, 3L, 3L, 3L, 3L, 3L, 4L, 3L, 4L, 3L, 4L, 4L, 
2L, 2L, 2L, 2L, 3L, 2L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 
1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 
1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 
1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 
1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 
1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 
1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 
1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 
1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 
1L, 1L, 1L, 1L, 1L, 1L), .Label = c("NA", "Low", "Medium", 
"High"), class = "factor")), .Names = c("date.time", "production", 
"ID", "ILP", "Class"), row.names = 649:864, class = "data.frame")

prod.data.list = list(prod.data1,prod.data2)

ID = c('D','O')
for(i in 1:length(ID)) {
prod.data = prod.data.list[[i]]
 s=     ggplot(prod.data, aes(x=date.time, y= production, fill = Class),binwidth=0) +
            geom_bar(stat = 'identity')+
            scale_fill_manual(values=c("#A8A8A8","#CCFF99", "#FFA31A", "#CC2900")) +
            scale_x_datetime()  +
            theme(legend.position = c(0.06,0.82), legend.key.height=unit(0.5,"line"),legend.key.width=unit(0.3,"line"),legend.background = element_blank(),legend.title = element_text("Class",size=8)) 


        f=  ggplot(prod.data, aes(x=date.time, y=ILP))  +
            geom_line() +
            geom_point() +
            scale_x_datetime()  

tiff(filename = paste0("Prod_Price_",as.Date(now()),ID[i],".tiff"), width=7,height=4.5,units="in", pointsize=12, bg = "white", res = 150, restoreConsole = TRUE)
        gs <- ggplotGrob(s)
        gf<- ggplotGrob(f)
        grid::grid.draw(rbind(gf, gs))
        dev.off()
    }

And this is an example of what I get (two graphs out of 20 ), any idea why I get hair line spaces between bars on the second graph? Why is the pattern so regular? Thanks for your help!

First example

Second example

The dataset is quite large (the prod.data and price.data dataframes get created for each iteration in the loop - i intentionally omited the 10+ lines of codes here), so i'm very sorry not to be able to reproduce the structure of the dataframe here... plus if I create something from scratch you may not see the effect of what I just described above. I'd like to understand why the same code yield different results - if anyone has an explanation i'd like to hear it. — Mathieu, Jun 09 '16 at 15:36
It might be hard to figure out without being able to use data and code that reproduces the problem. For now, I don't think `binwidth=0` does anything inside the main `ggplot` call and `binwidth` isn't an appropriate parameter inside `geom_bar` because the data are already binned in your case (due to `stat="identity"`). What happens if you add `width=1` inside `geom_bar`? — eipi10, Jun 09 '16 at 15:45
Also, when you save the graphs, I think you can just do `gridExtra::grid.arrange(f,s)`. — eipi10, Jun 09 '16 at 15:49
Thanks for your suggestions Eipi10, much appreciated. I understand that not giving a reproducible example is not a good practice and again I apologize for that. Adding the width=1 command in the geom_bar() function resulted in no bars being plotted. I use ggplotGrob() and grid.draw(rbind(gf,gs)) based on a suggestion i read on this forum because otherwise the time stamps between the two graphs don't exactly line up. Thanks for your help again. — Mathieu, Jun 09 '16 at 16:23
You don't need to provide your whole data frame. How about just providing, say, data for dates during June 9th for the two graphs you showed in your question? Paste into your question the output of `dput(data.subset)`. — eipi10, Jun 09 '16 at 16:52
Another suggestion: Sometimes issues like this occur due to finite pixel size of the graph and/or screen on which you view the graph. If you save the graphs as higher-resolution TIFFs or as PDF files and then view on your monitor, do you still see the vertical lines, and does the pattern differ between graphs? Make sure you zoom in quite a bit, just to make sure what you're seeing isn't an artifact of screen resolution. — eipi10, Jun 09 '16 at 16:58
Indeed. More simply trying exporting to a different file format like .png or .jpeg simply as a diagnostic tool. You'd at least be able to identify if the TIFF is the issue. — boshek, Jun 09 '16 at 16:59
Hi there, thanks for your suggestion, I added two examples of df generated in the loop. You sould be able to fully reproduce two graphs with the example above. I simplified the ggplot code a little, but barplot code was unchanged. One plot is correct (O) and one is faulty (D). Hope this helps. I tried png graphic device and I get the same results, with the same pattern in the lines. — Mathieu, Jun 09 '16 at 18:26

score 0 · Answer 1 · edited May 23 '17 at 11:58

Note that binwidth no longer works with geom_bar. From the docs:

geom_bar no longer has a binwidth argument - if you use it you'll get an warning telling to you use geom_histogram instead.

You managed to avoid the warning by using binwidth in ggplot instead of geom_bar, which made it hard to realize that it wasn't actually doing anything.

Use width in geom_bar to change the width of the bars. When working with factors, you would use width = 1 (as noted in the comments on your question) to get bars with no spaces between them. Things are a bit different when working with scale_*_datetime.

Per this answer, it turns out the datetime scale is in seconds, so width = 1 amounts to a bar width of 1 second. To get a bar width for 1 hour as in your data, you would need a width of 3600.

Using this gets rid of the spaces you see in your first example dataset.

ggplot(prod.data1, aes(x=date.time, y= production, fill = Class)) +
    geom_bar(stat = 'identity', width = 3600)+
    scale_fill_manual(values=c("#A8A8A8","#CCFF99", "#FFA31A", "#CC2900")) +
    scale_x_datetime()

eipi10 · Accepted Answer · 2016-06-09T22:27:46.967

Your issue relates to some combination of screen and plot resolution. Your plots actually have thin lines between every bar, but finite screen and/or plot resolution results in some of those spaces appearing and some not.

Here are two plots created with your sample data. I've used grid.arrange to lay them out and save them to an object. I removed the theme statement because I got an error when I tried to run it, but that shouldn't matter for the issue you're having (note, that binwidth=0 has no effect, but I've left in the code below):

pl = gridExtra::grid.arrange(
  ggplot(prod.data.list[[1]], aes(x=date.time, y= production, fill = Class),binwidth=0) +
    geom_bar(stat = 'identity')+
    scale_fill_manual(values=c("#A8A8A8","#CCFF99", "#FFA31A", "#CC2900")) +
    scale_x_datetime() + theme_bw() ,
  ggplot(prod.data.list[[2]], aes(x=date.time, y= production, fill = Class),binwidth=0) +
    geom_bar(stat = 'identity')+
    scale_fill_manual(values=c("#A8A8A8","#CCFF99", "#FFA31A", "#CC2900")) +
    scale_x_datetime() + theme_bw()
)

Okay, now let's save it to a PDF:

pdf("test.pdf", 8,2)
plot(pl)
dev.off()

Note that there's a space between every bar:

Now look at the same plot saved as a png with two resolutions:

png("test1.png", 1000,200)
plot(pl)
dev.off()

png("test2.png", 3000,600)
plot(pl)
dev.off()

As you can see, the first plot, at lower resolution shows some of the spaces between bars while in other cases the spaces are gone. The higher resolution plot shows all the spaces.

To get rid of the spaces, use width=3600 in geom_bar(because your bins are 1 hour = 3600 seconds wide, and POSIXct format is in seconds).

pl2 = gridExtra::grid.arrange(
  ggplot(prod.data.list[[1]], aes(x=date.time, y= production, fill = Class)) +
    geom_bar(stat = 'identity', width=3600)+
    scale_fill_manual(values=c("#A8A8A8","#CCFF99", "#FFA31A", "#CC2900")) +
    scale_x_datetime() + theme_bw() ,
  ggplot(prod.data.list[[2]], aes(x=date.time, y= production, fill = Class)) +
    geom_bar(stat = 'identity')+
    scale_fill_manual(values=c("#A8A8A8","#CCFF99", "#FFA31A", "#CC2900")) +
    scale_x_datetime() + theme_bw()
)

png("test3.png", 1000, 200)
plot(pl2)
dev.off()

png("test4.png", 3000, 600)
plot(pl2)
dev.off()

As you can see in each of the plots below, the spaces between bars are now gone in the upper panel, due to the change in width.

Thank you Eipi10 and AOsmith for investigating this, your explanations make a lot of sense. I'm really grateful that knowledgeable folks like you take time to help R users. Have a good weekend — Mathieu, Jun 09 '16 at 22:21

Barplot: Why do i get a variable spacing between bars in ggplot2 for identical script?

2 Answers2