Gnuplot Histogram Cluster (Bar Chart) with One Line per Category
bar-chart, gnuplot, histogram
Solution
After some research, I came up with two different solutions.
Required: Splitting the data file
Both solutions require splitting up the data file into several files categorized by a column. Therefore, I've created a short ruby script, which can be found in this gist:
https://gist.github.com/fiedl/6294424
This script is used like this: In order to split up the data file `data.csv` into `data.Category1.csv` and `data.Category2.csv`, call:
# bash
ruby categorize_csv.rb --column 2 data.csv
# data.csv
# year category num_of_events_for_A num_of_events_for_B
"2011";"Category1";"213";"30"
"2011";"Category2";"240";"28"
"2012";"Category1";"222";"13"
"2012";"Category2";"238";"42"
...
# data.Category1.csv
# year category num_of_events_for_A num_of_events_for_B
"2011";"Category1";"213";"30"
"2012";"Category1";"222";"13"
...
# data.Category2.csv
# year category num_of_events_for_A num_of_events_for_B
"2011";"Category2";"240";"28"
"2012";"Category2";"238";"42"
...
Solution 1: Stacked Box Plot
Strategy: One data file per category. One column per stack. The bars of the histogram are plotted "manually" by using the "with boxes" argument of gnuplot.
Upside: Full flexibility concerning bar sizes, caps, colors, etc.
Downside: Bars have to be placed manually.
# solution1.gnuplot
reset
set terminal postscript eps enhanced 14
set datafile separator ";"
set output 'stacked_boxes.eps'
set auto x
set yrange [0:300]
set xtics 1
set style fill solid border -1
num_of_categories=2
set boxwidth 0.3/num_of_categories
dx=0.5/num_of_categories
offset=-0.1
plot 'data.Category1.csv' using ($1+offset):($3+$4) title "Category 1 A" linecolor rgb "#cc0000" with boxes, \
'' using ($1+offset):3 title "Category 2 B" linecolor rgb "#ff0000" with boxes, \
'data.Category2.csv' using ($1+offset+dx):($3+$4) title "Category 2 A" linecolor rgb "#00cc00" with boxes, \
'' using ($1+offset+dx):3 title "Category 2 B" linecolor rgb "#00ff00" with boxes
The result looks like this:
Solution 2: Native Gnuplot Histogram
Strategy: One data file per year. One column per stack. The histogram is produced using the regular histogram mechanism of gnuplot.
Upside: Easier to use, since positioning has not to be done manually.
Downside: Since all categories are in one file, each category has the same color.
# solution2.gnuplot
reset
set terminal postscript eps enhanced 14
set datafile separator ";"
set output 'histo.eps'
set yrange [0:300]
set style data histogram
set style histogram rowstack gap 1
set style fill solid border -1
set boxwidth 0.5 relative
plot newhistogram "2011", \
'data.2011.csv' using 3:xticlabels(2) title "A" linecolor rgb "red", \
'' using 4:xticlabels(2) title "B" linecolor rgb "green", \
newhistogram "2012", \
'data.2012.csv' using 3:xticlabels(2) title "" linecolor rgb "red", \
'' using 4:xticlabels(2) title "" linecolor rgb "green", \
newhistogram "2013", \
'data.2013.csv' using 3:xticlabels(2) title "" linecolor rgb "red", \
'' using 4:xticlabels(2) title "" linecolor rgb "green"
The result looks like this:
References
- http://psy.swansea.ac.uk/staff/carter/gnuplot/gnuplot_time_histograms.htm
- Gnuplot: Multiple Stacked Histograms, each group using the same key
- http://gnuplot.sourceforge.net/docs_4.2/node249.html
Problem
Histogram Cluster / Bar Chart I'm trying to generate the following histogram cluster out of this data file with gnuplot, where each category is represented in a separate line per year in the data file: ``` # datafile year category num_of_events 2011 "Category 1" 213 2011 "Category 2" 240 2011 "Category 3" 220 2012 "Category 1" 222 2012 "Category 2" 238 ... ``` But I don't know how to do it with one line per category. I would be glad if anybody has got an idea how to do this with gnuplot. Stacked Histogram Cluster / Stacked Bar Chart Even better would be a stacked histogram cluster like the following, where the stacked sub categories are represented by separate columns in the datafile: ``` # datafile year category num_of_events_for_A num_of_events_for_B 2011 "Category 1" 213 30 2011 "Category 2" 240 28 2011 "Category 3" 220 25 2012 "Category 1" 222 13 2012 "Category 2" 238 42 ... ``` Thanks a lot in advance!