Gnuplot: categorised data - match color to data add range lines

Question

Given a set of values fitting into a category, I'd like to

a) plot the data values as dots (y axis) according to category (x axis) b) match dot color to category c) add a line ranging from minimum to maximum of each set

What I did, was using this code:

set terminal png 
set output 'animals.png'
set ytics nomirror
unset key
set xrange [-0.5:5.5]

plot for [i=2:5] 'cat.dat' using i:xtic(1)
show xrange

That successfully labels by category on the x-axis, but colors are set according to column (not row) and I would not know how to add the range bars (note: not errorbars or percentiles, but the full min->max range)- especially since the data is called columnwise but would then need to be analysed rowwise. AFAIK gnuplot does columns only, though.

Any ideas?

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Output with above code:

Example data (tab-delimited):

cat 0.26    0.4 0.23    0.16
dog 0.317   0.264   0.25    0.26
bat 0.33    0.42    0.32    0.48
rat 0.59    0.62    0.57    0.56
foo 0.59    0.67    0.71    0.70
bar 0.664   0.75    0.68    0.6

Answer 1

As you noticed, gnuplot doesn't like rows and unfortunately does not (yet?) offer a transpose function. In your solution, you are using Unix system calls/tools and sed, which are not necessarily platform independent. Furthermore, you are plotting points and separate arrows to connect, I guess you can simplify this by linespoints if you don't insist on a horizontal bar at the minimum and maximum values.

Let me show some "simplified" platform-independent gnuplot-only code.

General Procedure:

1. load file to datablock
2. transpose datablock
3. plot columns with linespoints

Datafile TAB-separated without header: Animals.dat

cat 0.26    0.4 0.23    0.16
dog 0.317   0.264   0.25    0.26
bat 0.33    0.42    0.32    0.48
rat 0.59    0.62    0.57    0.56
foo 0.59    0.67    0.71    0.70
bar 0.664   0.75    0.68    0.6

The code below requires a FileToDatablock routine and a DatablockTranspose routine.

Procedure to load file into datablock: FileToDatablock.gpp

### Load datafile "as is" into datablock for different platforms
# ARG1 = input filename
# ARG2 = output datablock

if (GPVAL_SYSNAME[:7] eq "Windows") {          # "Windows_NT-6.1" is shown on a Win7 system
    load '< echo '.ARG2.' ^<^<EOD & type "'.ARG1.'"'
}
if (GPVAL_SYSNAME eq "Linux") {                # that's shown on a Raspberry
    load '< echo "\$Data << EOD" & cat "'.ARG1.'"'
}
if (GPVAL_SYSNAME eq "Darwin") {               # this was shown on a MacOS Sierra 10.12.6
    load '< echo "\$Data << EOD" & cat "'.ARG1.'"'  # identical to Linux
}
### end of code

gnuplot procedure for transposing a datablock: DatablockTranspose.gpp

### transpose datablock (requires whitespace as separator)
# ARG1 = Input datablock
# ARG2 = Output datablock

set print @ARG2
do for [DBT_i=1:words(@ARG1[1])] { 
    DBT_Line = ""
    do for [DBT_j=1:|@ARG1|] {
       DBT_Line = DBT_Line.word(@ARG1[DBT_j],DBT_i).\
       (DBT_j < |@ARG1| ? "\t" : "")
    }
    print DBT_Line
}
set print
undefine DBT_*
### end of code

The actual code:

### plotting rows
reset session

# load file to datablock
call "FileToDatablock" "Animals.dat" "$Data"

# transpose datablock by gnuplot procedure
call "DatablockTranspose.gpp" "$Data" "$DataTransposed"

set palette defined ( 0 'purple', 1 'blue', 2 'green', \
    3 'yellow', 4 'orange', 5 'red' , 6 'black' )
unset colorbox

set xrange[0.5:|$Data|+0.5]
plot for [i=1:|$Data|] $DataTransposed u (i):i:(i):xtic(columnhead(i)) w lp pt 7 ps 1.5 lc palette not
### end of code

The result:

Answer 2

This takes a few more steps, above all, each category is given a unique index number, and the data is transposed:

(I'll refer to GNU unix shell commands here)

$cat -n data_orig.dat | datamash transpose > data_trans.dat
$cat data_trans.dat  #added spaces for readability

     1       2       3       4       5       6
cat     dog     bat     rat     foo     bar
0.26    0.317   0.33    0.59    0.59    0.664
0.4     0.264   0.42    0.62    0.67    0.75
0.23    0.25    0.32    0.57    0.71    0.68
0.16    0.26    0.48    0.56    0.70    0.6

Now the data can be properly analyzed in columns and colors be defined according to the index number. The bars are made with arrows, where minimum and maximum are taken from the statistical analysis of each column. The xticlabels are read into a 1D word array (this is an internal gnuplot function) with a system call and the array indices are made to match the unique indices of the data columns.

The script with very detailed explanations to better support new gnuplot users:

#output and style settings: make png-file, name it 'animals.png',
#   yaxis tics on both sides, no legend
set terminal png 
set output 'animals.png'
set ytics mirror
unset key

#data indices are integers from 1 to 6, a bit of space for the looks
set xrange [0.5:6.5] 

#define color scheme for each data series
set palette defined ( 0 'purple', 1 'blue', 2 'green', \
    3 'yellow', 4 'orange', 5 'red' , 6 'black' )

#hide color gradient bar of palette
unset colorbox

#define array names using word function:
#  read in 2nd line of data by system call and run through words
#  each space-delimited word is now an array element of names
names(n) = word( system("sed -n '2p' cat.dat_t" ) , n )

#create min->max bars
#loop over all data sets to create bars
do for [i=1:6] {

    #among others this gives minimum and maximum values of the data set
    #using i -> only handle column i in statistics
    #every ::3 start with row 3 for statistical analysis
    stats 'data_trans.dat' using i every ::3

    #use min/max values for arrow y positions, index i for x positions
    #heads = arrow head on both sides
    #size 0.1,90 = 0.1 line lengths for arrow head
    #          and 90° arrow head line angles = T bar style
    #lc palette cb i = use line color (lc) from palette value matching
    #   color bar (cb) value of index i
    set arrow from i,STATS_min to i,STATS_max heads size 0.1,90 lc palette cb i

}

#plotting:
#   for [i=1:6] loop over all 6 columns, use i as loop variable
#   every ::3 start with row 3 for data plotting
#   using (i):i:(i):xtic(names(i))
#         syntax of using
#         x-value:y-value:z-value:label_x_axis [:label_y_axis:label_z_axis]
#         (i) -> literal value of i for x and z, z is used as color definition
#         i -> y-values from column i
#         xtic(names(i)) get element i of array names for xtic label
#   lc palette -> coloring according to defined palette
#   pt 7 ps 1.5 -> point style and size definition
plot for [i=1:6] 'data_trans.dat' every ::3 using (i):i:(i):xtic(names(i)) lc palette pt 7 ps 1.5

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References:

coloring based on x-values

array from word function

Result:

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EDIT:

As shown in @theozh 's answer, linespoints are far more practicable for showing the range. This allows skipping the whole bar/arrow creation block by just adding w lp in the plotting command line.