Plot from two files with errorbars for Gnuplot

Question

I am thinking which way to do the addition of errorbars better by thinking the format of data. The standard way of adding errors bars is discussed here, for instance.

My original data is in ranges

Model Decreasing Constant Increasing 
2025 73-78 80-85 87-92 
2035 63-68 80-85 97-107 
2050 42-57 75-90 104.5-119.5

where the values are ranges. I cannot plot directly in Gnuplot so I have to split it to averages and to error values in two files:

Averages:

Model Decreasing Constant Increasing
2025 75.5 82.5 89.5
2035 65.5 82.5 102
2050 49.5 82.5 112

and error configuration in ybar

Model Decreasing Constant Increasing
2025 2.5 2.5 2.5
2035 2.5 2.5 5
2050 7.5 7.5 7.5

I normally plot data like this as a one file

plot for [i=2:4] 'data.dat' using 1:i w linespoints

but now I should go through two files at the same time while doing the plot. The normal syntax of plotting errorbars is

plot 'data' using 1:2:0:($1+$3):4:5 with yerrorlines

and manual here.

How can you plot from two files with errorbars in Gnuplot? Feel free to propose if you know better way to do the addition of these errorbars in gnuplot.

Output to Cristoph's answer

enter image description here

where error bars missing in the first and third points.

sweber sweber · Accepted Answer · 2015-04-18T20:55:54

First of all, I wonder about your columns used for plotting with yerrorlines. If your first data for 2025 is 75.5+/-2.5, you usually plot it with

plot "datafile" using <xcolum>:<ycolum>:<yerrorcolumn>

Your six columns are for the case of xy errorbars and specify the point itself and the lower and upper absolute values in x and y. But may be you are just doing it as you need it...

Now back to your question: Gnuplot can not handle data from two files simultaneously, i.e. it can not take xy-values from one file and y-errors from another.

If you're running linux, the command line tool join can help. Your averages stored in file A and the errors in file B, join A B will concatenate lines with the same value in the first colum like this:

2025 75.5 82.5 89.5 2.5 2.5 2.5

So,

plot "<join A B" using 1:2:5 with yerrorlines

should do the job. ("<join A B" will call the join command in the background and read its output like a data file)

Plot from two files with errorbars for Gnuplot

Output to Cristoph's answer

2 Answers