Re: [Gnuplot-info] transpose data with gnuplot

[Ethan A M. <eam...@gm...>]

On Wednesday, 07 November 2018 08:13:40 theozh wrote:
> sometimes, data curves are available in rows and since gnuplot requires data in columns you would have to transpose your data, correct?
> 
> Of course, you can transpose your data with external tools (Python, awk, ...), however, in some cases it might be easier to do this in gnuplot.
> I am not aware of a function in gnuplot which plots rows or a function which transposes data.

Obscure commands
================

plot nth row of data in a file
        plot 'rowdata' matrix using 1:0 every :::n::n
     
store row n to an array, then plot it
        array row_n[10]
        stats 'rowdata' matrix using 1:(row_n[$1+1]=$0,$0) every :::n::n
        plot row_n

These commands arose unintentionally out of the way "every" interacts with
"matrix". So far as I know they are undocumented, but the behavior is not
likely to change.

    cheers,

		Ethan


> So, I created the script below.
> I think it is neither very elegant nor efficient, but is seems to work.
> However, if you have to load the data from a file and transpose it this file needs to be loaded "Rows x Cols" times for every datapoint. Is it like that or will the file be kept in memory? This will be problematic if you have to load the data from a slow network drive.
> If anybody has a better solution please let me know.
> 
> The script below will 1) create some dummy data 2) print the data 3) transpose it 4) print the transposed data
> 
> ### transpose data
> reset session
> 
> # create some dummy data
> Rows = 5
> Cols = 7
> set print $Data 
> LINE = sprintf("%gx%g\t",Rows,Cols)
> # create header columns
> do for [j=1:Cols] {
>     LINE = LINE.sprintf("x[%g]",j)
>     if (j<Cols) {LINE = LINE."\t"}
> }
> print LINE
> do for [i=1:Rows] {
>     LINE = ""
>     do for [j=1:Cols] {
>         LINE = LINE.sprintf("%g", (i-1)*Cols + j)
>         if (j<Cols) {LINE = LINE."\t"}
>     }
>     LINE = sprintf("t[%g]\t",i).LINE
>     print LINE
> }
> set print
> print $Data 
> # end dummy data
> 
> # transpose data
> set autoscale    # autoscale before stats
> stats $Data u 0 nooutput
> set table $Dummy
> set print $Transposed
> do for [i=1:STATS_columns] {
>     LINE = ""
>     do for [j=0:STATS_records-1] {
>        plot $Data u (a=stringcolumn(i),i) every ::j::j with table
>        LINE = LINE.sprintf("%s", a)
>        if (j < STATS_records-1) {LINE = LINE."\t"}
>     }
>     print LINE
> }
> set print
> unset table
> print $Transposed
> # end transpose data