Remove space between bars within a grid

Question

I want to move bars that are within one grid closer to save space. Is there a way to do that? The code I used just change the bar width and does not change the spacing. I am aware that bindwidth no longer work in geom_bar as I referred to these problems:

Adding space between bars in ggplot2 Increase space between bars in ggplot

This is the data

dput(grp1)
structure(list(Rot = structure(c(1L, 1L, 1L, 1L, 2L, 2L, 2L, 
2L, 2L, 2L, 3L, 3L, 3L, 3L, 3L, 3L, 3L, 3L), .Label = c("2-year", 
"3-year", "4-year"), class = "factor"), Rot.Herb = structure(c(3L, 
4L, 13L, 14L, 5L, 6L, 9L, 10L, 15L, 16L, 1L, 2L, 7L, 8L, 11L, 
12L, 17L, 18L), .Label = c("A4-conv", "A4-low", "C2-conv", "C2-low", 
"C3-conv", "C3-low", "C4-conv", "C4-low", "O3-conv", "O3-low", 
"O4-conv", "O4-low", "S2-conv", "S2-low", "S3-conv", "S3-low", 
"S4-conv", "S4-low"), class = "factor"), Rot.trt = structure(c(2L, 
2L, 7L, 7L, 3L, 3L, 5L, 5L, 8L, 8L, 1L, 1L, 4L, 4L, 6L, 6L, 9L, 
9L), .Label = c("A4", "C2", "C3", "C4", "O3", "O4", "S2", "S3", 
"S4"), class = "factor"), Crop = structure(c(2L, 2L, 4L, 4L, 
2L, 2L, 3L, 3L, 4L, 4L, 1L, 1L, 2L, 2L, 3L, 3L, 4L, 4L), .Label = c("alfalfa", 
"corn", "oat", "soybean"), class = "factor"), Year = c(2014L, 
2014L, 2014L, 2014L, 2014L, 2014L, 2014L, 2014L, 2014L, 2014L, 
2014L, 2014L, 2014L, 2014L, 2014L, 2014L, 2014L, 2014L), Herb.trt = structure(c(1L, 
2L, 1L, 2L, 1L, 2L, 1L, 2L, 1L, 2L, 1L, 2L, 1L, 2L, 1L, 2L, 1L, 
2L), .Label = c("conv", "low"), class = "factor"), variable = structure(c(1L, 
1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 
1L), .Label = "kg.ha", class = "factor"), N = c(4, 4, 4, 4, 4, 
4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4), value = c(0.43168573275, 
16.22463846275, 0.554446363, 25.89844593075, 13.882743364, 84.1922080725, 
84.2625, 105.7375, 0.8350420895, 106.7464386085, 127.8875, 65.3875, 
1.964170084, 29.46524929925, 249.7625, 333.125, 0.535560112, 
28.757014893), sd = c(0.528135488290589, 20.3216237207314, 0.8810357408252, 
40.4576156325903, 27.3195114207629, 71.6424882235524, 22.6948736869511, 
40.9587266851237, 0.931926987921512, 108.45555847826, 89.1035387905553, 
25.141843442092, 2.20017281317418, 24.1072626208021, 93.2983509589889, 
85.0439543216722, 0.48339034731648, 33.2628789566726), se = c(0.264067744145294, 
10.1608118603657, 0.4405178704126, 20.2288078162951, 13.6597557103815, 
35.8212441117762, 11.3474368434756, 20.4793633425619, 0.465963493960756, 
54.2277792391299, 44.5517693952777, 12.570921721046, 1.10008640658709, 
12.0536313104011, 46.6491754794945, 42.5219771608361, 0.24169517365824, 
16.6314394783363), ci = c(0.840381416699796, 32.3362381637038, 
1.40192446910603, 64.3770946952626, 43.4714390915815, 113.999185974188, 
36.112608456959, 65.1744742040986, 1.48290379975249, 172.576995683309, 
141.783613905853, 40.0062833851536, 3.50096592013592, 38.3600344290379, 
148.458496149248, 135.323909108861, 0.76918191241357, 52.928663119381
)), .Names = c("Rot", "Rot.Herb", "Rot.trt", "Crop", "Year", 
"Herb.trt", "variable", "N", "value", "sd", "se", "ci"), row.names = c(NA, 
-18L), class = "data.frame")

This is the code

ggplot(grp1, aes(x=Rot.Herb, y=value, fill=factor(Herb.trt)))+
  geom_bar(stat="identity", position=position_dodge(.), width=.5)+
  scale_fill_brewer(palette = "Dark2")+
  theme_bw() +
  theme(panel.grid.major=element_blank()) +
  facet_grid(~Crop, scales = "free_x", space="free_x")+
  theme(legend.title=element_blank(),legend.text=element_text(size=20),legend.position="top")+
  geom_errorbar(aes(ymin=value-se, ymax=value+se), size=0.75, width=.25,position=position_dodge(.5))+
  xlab("Treatment") +
  theme(axis.title = element_text(size=24,face="bold", vjust=4)) +
  ylab("2014 total weed biomass (Kg/ha)\n") +
  theme(axis.title = element_text(size=24,face="bold", vjust=2), axis.text.y = element_text(size=20, color="black"))+
  theme(strip.text.x = element_text(colour = "black", size = 15), strip.background = element_rect(fill = "white"), axis.text.x = element_blank(), axis.ticks.x = element_blank())

And graph

What I want is a graph with bar width of 0.5 and no spacing between bars in the same grid. Thank you for all the input.

Thanks for responding. I wanted to use that dot to remove space between bars. — Little Bee, Oct 24 '16 at 19:28
The `width` parameter adjusts what proportion of the space between bars is filled. `width = 1` means 100% of the space is fulled (no space between bars), `width = 0.5` means the bars are 50% of the width they would be if they were touching. So you've got a problem, because you want both the bars to touch and you want the bars to be half the width they would need to be to touch. — Gregor Thomas, Oct 24 '16 at 19:38
Maybe a better question for you would be to ask what you *don't* like about the plot when you set `width = 1`? Because that's how you remove the space between the bars. — Gregor Thomas, Oct 24 '16 at 19:40
Also note that `bindwidth` is tangential to this question since your data are pre-binned. — Gregor Thomas, Oct 24 '16 at 19:43

acylam · Accepted Answer · 2017-09-05T03:16:27.027

I think you want width = 0.5 while keeping the bars touching because you don't want the absolute width to change (width = 0.5 changes the relative width). This might be closer to what you are asking for.

ggplot(grp1, aes(x=Rot.Herb, y=value, fill=factor(Herb.trt)))+
  geom_bar(stat="identity", position = "dodge", width=1)+
  scale_x_discrete(expand=c(0.2,0))+
  scale_fill_brewer(palette = "Dark2")+
  theme_bw() +
  theme(panel.grid.major=element_blank()) +
  facet_grid(~Crop, scales = "free_x", space="free_x")+
  theme(legend.title=element_blank(),legend.text=element_text(size=20),legend.position="top")+
  geom_errorbar(aes(ymin=value-se, ymax=value+se), size=0.75, width=.25,position=position_dodge(0.5))+
  xlab("Treatment") +
  theme(axis.title = element_text(size=24,face="bold", vjust=4)) +
  ylab("2014 total weed biomass (Kg/ha)\n") +
  theme(axis.title = element_text(size=24,face="bold", vjust=2), axis.text.y = element_text(size=20, color="black"))+
  theme(strip.text.x = element_text(colour = "black", size = 15), strip.background = element_rect(fill = "white"), axis.text.x = element_blank(), axis.ticks.x = element_blank())

Basically I changed the width = 1 as suggested by @Gregor, which causes the bars to touch, but added an extra option scale_x_discrete(expand=c(0.2,0)) to add spaces between the bars and the sides of the plot. This in effect adjusts the absolute width of the bars while keeping them touching. The first number gives the multiplicative constant used to expand the range, while the second gives the additive.

You can experiment with the two values in expand = to get what you want.

Also see this related question: ggplot geom_boxplot: reduce space between x-axis categories

Remove space between bars within a grid

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