Iteratively generate datablocks in gnuplot

Question

Is it possible to iteratively generate datablocks, where the name of the datablock is build up inside the loop? Let's assume I have three fruits (in reality there are more):

array namelist[3] = ['apple', 'banana', 'pineapple']

I want to create three datablocks with the names $apple_data, $banana_data and $pineapple_data, so I tried the following:

do for [i=1:|namelist|] {
set table '$'.namelist[i]."_data"
plot ...
unset table
}

Unfortunately, instead of datablocks gnuplot created files with these names in the working directory. I guess gnuplot is checking whether the first character after set table is a $?

My second attempt was to remove the apostrophes around $:

set table $.namelist[i]."_data"

But this raised the weird error "Column number or datablock line expected", pointing at the period right after $.

Any ideas on how to achieve that? The reason for all this is that I read in the banana/apple data files with a lengthy path, apply some lengthy calculations within using, and reuse these for lots of successive stats and plot commands. I would like to avoid having to hard-code and copy-paste the same long path and the cumbersome using command over and over again.

Answer 1

Not sure if I fully understood your detailed intention. If you only want to avoid typing (or copy pasting) a lengthy path again and again, simply use variables:

FILE1 = 'C:/Dir1/SubDir1/SubSubDir1/SubSubSubDir1/File1' 
FILE2 = 'C:/Dir2/SubDir2/SubSubDir2/SubSubSubDir2/File2'
plot FILE1 u 1:2, FILE2 u 1:2

Anyway, you asked for dynamically generated datablocks. One way which comes to my mind is using evaluate, check help evaluate. Check the example below as a starting point, which can probably be simplified.

Code: (simplified thanks to @Eldrad's comment)

### dynamically generate some datablocks
reset session

myNames   = 'apple banana pineapple'
myName(i) = word(myNames,i)

N = words(myNames)
set samples 11

do for [i=1:N] {
    eval sprintf('set table $%s_data',myName(i))
        plot '+' u 1:(rand(0)) w table
    unset table
}

plot for [i=1:N] sprintf('$%s_data',myName(i)) w lp pt 7 ti myName(i)
### end of code

Result: