GNUPLOT draws step plot not within border restrictions

Question

Drawing a step plot leads always to an out of border result.
How to solve the issue? Any ideas? THX!

The MWE is:

reset;set term png small size 500,500;set output 'test.png';
set title 'First step is always drawn out of chart borders ?!?';
unset y2tics;set y2range [0:40];set y2tics 10;set yrange [0:40];set ytics 10 mirror;
set style fill solid 1.00 border;
plot 'test.data' using 1:2  notitle with fillsteps lc rgb 'light-goldenrod', \
'' using 1:3 notitle with fillsteps lc rgb 'gray40', \
'' using 1:4 notitle with fillsteps lc rgb 'web-green', \
'' using 1:5 notitle with fillsteps lc rgb 'light-green';

The result is:

Used software is:

GNUPLOT Version 5.2 patchlevel 8

Answer 1

Ok, now I see your point. Looks like a little bug (or our limited understanding). I cannot tell right away why this is, but you can avoid it by adding a line in the beginning which contains the first x value and all y-values are 0. If you don't want to do this manually, there would be ways to do this automatically with gnuplot. But I hope there is a simpler solution.

Code:

### plot with fillsteps
reset session

$Data <<EOD
1    0   0   0   0
1   50  35  30   5
2   55  30  20   5
17  51  44  30  12
20   1   1   1   1
EOD

unset y2tics;set y2range [0:40]
set y2tics 10
set yrange [0:40]
set ytics 10 mirror
set style fill solid 1.00 border
unset key

plot $Data u 1:2 w fillsteps lc 'light-goldenrod', \
        '' u 1:3 w fillsteps lc 'gray40', \
        '' u 1:4 w fillsteps lc 'web-green', \
        '' u 1:5 w fillsteps lc 'light-green'
### end of code

Result:

Addition: (automatically duplicate first line, to workaround the bug(!?))

In order to workaround this (what I would call unexpected or a bug) you want to duplicate the first line automatically. There would be certainly different easy ways with external tools, however, which would not guarantee platform-independence. So, here is one of several possible gnuplot-only solutions.

1. get your file into a datablock (here: $Data) (see gnuplot: load datafile 1:1 into datablock)
2. print the first line of $Data into a new datablock (here: $Data2) Make sure that the first line is not a header or commented line, i.e. print the first dataline.
3. append the full datablock $Data again to $Data2.

Data: (Test.dat)

1   50  35  30   5
2   55  30  20   5
17  51  44  30  12
20   1   1   1   1

Code: (Result same as above)

# https://stackoverflow.com/a/67151340/7295599
### plot with filledcurves
reset session

FileToDatablock(f,d) = GPVAL_SYSNAME[1:7] eq "Windows" ? \
                       sprintf('< echo   %s ^<^<EOD  & type "%s"',d,f) : \
                       sprintf('< echo "\%s   <<EOD" & cat  "%s"',d,f)     # Linux/MacOS

FILE = 'Test.dat'
load FileToDatablock(FILE,'$Data')

set print $Data2
    print $Data[1]   # only first line
    print $Data
set print

unset y2tics;set y2range [0:40]
set y2tics 10
set yrange [0:40]
set ytics 10 mirror
set style fill solid 1.00 border
unset key

plot $Data2 u 1:2 every ::0::0 w fillsteps lc 'light-goldenrod', \
        '' u 1:2 w fillsteps lc 'light-goldenrod', \
        '' u 1:3 w fillsteps lc 'gray40', \
        '' u 1:4 w fillsteps lc 'web-green', \
        '' u 1:5 w fillsteps lc 'light-green'
### end of code