gnuplot : variable paths to data file in a for loop - for-loop

Question

I would like to plot multiple curve on the same graph using a for loop. Each data file (named stat_coupe) is located in a different folder (fwal055wal055/rep16/ and fwal055wal055_c2/rep20/). fwal055wal055 and fwal055wal055_c2 correspond to names of simulation. First, I need to get a previous result, a single number (Utau), in other files (named file_fwal055wal055 and file_fwal055wal055_c2). This is successfully done thanks to the command awk. The result depend on the file: Utaufwal055wal055=10.5 and Utaufwal055wal055_c2=12.2.
Then I need to divid the 1st column of the file stat_coupe corresponding to the path fwal055wal055/rep16/ by the value of Utaufwal055wal055 and do the same thing for the file stat_coupe corresponding to the path fwal055wal055_c2/rep20/ with the value of Utaufwal055wal055_c2. Moreover, each plot should have a specific format which depend on the type of simulation run (fwal055wal055 or fwal055wal055_c2).
The presented problem is reduced to 2 simulations fwal055wal055 and fwal055wal055_c2 and 1 plot but I have about 20 simulations and 15 various graphs to plot that is why I would like to use the for loop.
To summary at each iteration I have:
a specific format,
a specific path,
a specific value of Utau
I want to indicate the wright format, path and value of Utau at each iteration of the for loop. The solution I propose below successfully permits to obtain the value of Utau for each simulation but the code #path_.i and #format_.i does not work.
#!/bin/bash
for elem in fwal055wal055 fwal055wal055_c2;
do
Utau[${elem}]=$(awk 'FNR==5{print $1}' file_$elem)
done
gnuplot -persist <<-EOFMarker
format_fwal055wal055='pt 1 ps 1.0 lc 0 title "WALE"'
format_fwal055wal055_c2='pt 2 ps 1.0 lc 0 title "WALE c2"'
path_fwal055wal055='"fwal055wal055/rep16/stat_coupe"'
path_fwal055wal055_c2='"fwal055wal055_c2/rep20/stat_coupe"'
list="fwal055wal055 fwal055wal055_c2"
plot for [i in list] #path_.i u 1:(\$2/${Utau[${i}]}) #format_.i
EOFMarker
I would like to obtain something equivalent to:
plot #path_fwal055wal055 u 1:(\$2/${Utau[${i}]}) #format_fwal055wal055,\
#path_fwal055wal055_c2 u 1:(\$2/${Utau[${i}]}) #format_fwal055wal055_c2
Can someone help me to solve this issue ?
Thank you very much,
Martin

Answer 1

Check help sprintf, help words and help word.
I would create two strings with the same number of items and then combine them with sprintf(). From gnuplot 5.2 on you could also do it with arrays.
# Version 1
PATHS = '"fwal055wal055/rep16/stat_coupe" "fwal055wal055_c2/rep20/stat_coupe"'
FILES = "fwal055wal055 fwal055wal055_c2"
plot for [i=1:words(FILES)] sprintf("%s_%s",word(PATHS,i),word(FILES,i)) u 1:2
or you could define a function for your filenames to keep the plot command short and readable.
# Version 2
PATHS = '"rep16/stat_coupe" "rep20/stat_coupe"'
FILES = "fwal055wal055 fwal055wal055_c2"
myFilename(i) = sprintf("%s/%s_%s",word(FILES,i),word(PATHS,i),word(FILES,i))
plot for [i=1:words(FILES)] myFilename(i) u 1:2
Addition (after some clarifications...)
If I understand your question now correctly, the following code should do the job.
For the extraction of the UTAUS you do a separate loop before plotting and store the extracted values in a string. During plotting you get these values back via word(UTAUS,i). Since you do the mathematical operation column(2)/word(UTAUS,i), gnuplot will interpret them as number. Check help words, help word, help sprintf, help every.
Code:
### extract and normalize in a loop with individual files and directories
reset session
FILES = 'fwal055wal055 fwal055wal055_c2'
DIRS = 'rep16 rep20'
TITLES = '"WALE" "WALE c2"' # if you have spaces you need to put it into double quotes
UTAUS = ''
# define functions for better readability
myExtractionFile(i) = sprintf("file_%s",word(FILES,i))
myDataFile(i) = sprintf("%s/%s/stat_coupe",word(FILES,i),word(DIRS,i))
myTitle(i) = word(TITLES,i)
# define point or line appearance. Add more if you have more files
set style line 1 pt 1 ps 1.0 lc 0
set style line 2 pt 2 ps 1.0 lc 1
# extract the UTAUs
do for [i=1:words(FILES)] {
set table $Dummy
plot myExtractionFile(i) u (utau=$1) every ::4::4 w table # extract value row 5, column 1 (not counting header lines)
unset table
UTAUS = UTAUS.sprintf(" %g",utau) # append the extracted value as string
}
plot for [i=1:words(FILES)] myDataFile(i) u 1:(column(2)/word(UTAUS,i)) ls i title myTitle(i)
### end of code