gnuplot: How to put legends outside of each plot in a multiplot? - plot

Question

I would like to put the legend of each plot outside on the top of them.
I'm using multiplot ,so the problem is that when i try to do this all the legends end up at the top of the figure.
How can I put each legend on top of the corresponding plots ?
Hers is a sample of my code
reset
set datafile separator comma
set term pdfcairo enhanced font "Helvetica,7" size 4,7
set output "data.pdf"
set multiplot layout 6,2 margins 0.07, 0.95, 0.05, 0.97 spacing 0.1,0.05
set tics nomirror
set grid xtics ytics lt 1 lw 0.5 lc rgb "grey"
############################################ PLOT
set key outside horizontal
set ylabel "V [mV]"
set label "A" at graph -0.14,1.1
plot "data.txt" using "time":"V" with lines
unset label
plot "data.txt" using "time":"V" with lines
unset ylabel
############################################# PLOT
set key outside horizontal
set label "B" at graph -0.14,1.1
set ylabel "I_{tot} [pA/pF] "
plot "data.txt" using "time":"Itotal" with lines
unset ylabel
unset label
unset key
############################################ PLOT
set key outside horizontal
set label "G" at graph -0.16,1.1
set ylabel "J_{rel} [mM/s]"
plot "data.txt" using "time":"Jrel" with lines
unset ylabel
unset label
unset key
unset multiplot
And here is the image produced (by the complete code)

Answer 1

Check the following 3 variations of a minimal example.
Variation 1 has different sizes of the subplots, that's not what you wanted.
In variation 2, I would consider the behaviour of the key as unexpected and as a bug.
The third (cumbersome) variation probably comes close to what you expected.
Code:
### multiplot version with undesired auto margins but correct keys
reset session
set key out horizontal
set multiplot layout 3,3 spacing 0.1,0.1
do for [i=1:9] {
plot x**i title sprintf("x**%d",i) lc i
}
unset multiplot
pause -1 "Press Enter to continue"
### multiplot version with desired margins but wrong keys
reset session
set key out horizontal
set multiplot layout 3,3 margin 0.07, 0.93, 0.07, 0.93 spacing 0.1,0.1
do for [i=1:9] {
plot x**i title sprintf("x**%d",i) lc i
}
unset multiplot
pause -1 "Press Enter to continue"
### version with desired margins and correct keys (but cumbersome)
reset session
set key out horizontal
myLmargin = 0.07
myRmargin = 0.93
myBmargin = 0.07
myTmargin = 0.93
myXspacing = 0.1
myYspacing = 0.1
Rows=3 # rows
Cols=3 # columns
myWidth = (myRmargin-myLmargin-(Cols-1)*myXspacing)*1./Cols
myHeight = (myTmargin-myBmargin-(Rows-1)*myYspacing)*1./Rows
# myPosX(n) = myLmargin + n*(myWidth + myXspacing)
# myPosY(m) = myTmargin - (row+1)*myHeight - 0.5*myYspacing
myLmarg(row,col) = myLmargin + col*(myWidth + myXspacing)
myRmarg(row,col) = myLmargin + (col+1)*myWidth + col*myXspacing
myBmarg(row,col) = myTmargin - (row+1)*myHeight - row*myYspacing
myTmarg(row,col) = myTmargin - row*(myHeight + myYspacing)
set multiplot
do for [row=0:Rows-1] {
do for [col=0:Cols-1] {
set origin myLmarg(row,col), myBmarg(row,col)-0.5*myYspacing
set size 1,1./Rows
set lmargin screen myLmarg(row,col)
set rmargin screen myRmarg(row,col)
set bmargin screen myBmarg(row,col)
set tmargin screen myTmarg(row,col)
j = row*Cols + col + 1
plot x**j title sprintf("x**%d",j) lc j
}
}
unset multiplot
### end of code
Result 1: (undesired auto margins, i.e. different subplot sizes, but correct keys)
Result 2: (desired margins and equal subplot sizes, but wrong overlapping keys)
Result 3: (desired margins and sizes and correct keys, but "manual" settings)