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I just discover gnuplot 4.6 and the beautiful loop tool. I want to plot a curve with different x axis, but it doesnt work. I have a file called file.txt, where there is a list of data like :

E002 = ...

E003 = ...

.

.

.

E021 = ...

The point is to shift the x axis of each plot with the corresponding data, something like this : 

load 'file.txt'
plot for [a=2:21] 'my_data_file.dat' u ($1+'E00'.a ):a w l

But this doesn't work, and I have the error : 'Non-numeric string found where a numeric expression was expected'.

I do not know how to bypass this issue.

Second question, i would like after to sum all the column but shifted like before. Something like :

($1+E002):$2 + ($1+E003):$3 +...

Is there a way to do that ?

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For the first question, you need to use the value to get the value of a variable.

I suggest to use a more versatile sprintf command to manipulate strings:

plot for [a=2:21] 'my_data_file.dat' u ($1+value(sprintf('E%03d',a))):a w l

Type help value and help sprintf to get more info about those commands

I don't understand very well the second question, maybe something like this could help?

my_sum=0
plot for [a=2:21] my_val=value(sprintf('E%03d',a)), my_sum=my_sum+my_val, 'my_data_file.dat' u ($1+my_val):a w l

print my_sum

the last line, should print the sum of all you Exxx values.

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4 Comments

THANKS, the first solution is working !!! Regarding the second question, i want to sum the value in each column ($2+$3+...) and plot it but i want that the value (if we consider $2 like a fonction): $2 ($1+E002) +$3($1+E003). DO you know what i mean ?
sorry it's still unclear... particularly the part (if we consider $2 like a fonction): $2 is the second column of your data... in your question you say ($1+E002):$2 + ($1+E003):$3 +... this is the sum of two plots? try to write a script for just 2-3 columns and we'll se if with loops we can extend to any column size
Okay, if i have a function f and an other function g, i can plot easily f(x+E002) + g(x+E003) along x. So if i have many different functions, i can sum them with a loop or not and plot the sum. I wat to do the same but not with function, with my columns. I want to plot the sum of each column but shifted like for the function. I do not know if it is possible with column, even with only two.
Still unclear, but does this imply that you need to interpolate the values?

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