I would like to fit a function using many data sets. For example, I reproduce an experience many times, each time I obtain a pair of data column (x,y). I put all these column in a file named 'data.txt' :
first experience : x = column 1, y = column 2
second experience : x = column 3, y = column 4
third experience : x = column 5, y = column 6
...
Now I wish to fit a function y = f(x) for these data sets. I do not know if Gnuplot can do that ? If it is possible, could you please help me to correct the following command ? This one does not work.
fit f(x) "data.txt" u 1:2:(0.25), "data.txt" u 3:4:(0.25), "data.txt" u 5:6:(0.25) via a, b
You can process your data so that columns 1, 3 and 5 all become the same column 1, and columns 2, 4 and 6 all become the same column 2. It's easy with awk, you can do it outside gnuplot:
awk '{print $1, $2} {print $3, $4} {print $5, $6}' data.txt > data2.txt
and then fit it within gnuplot:
f(x)=a*x+b
fit f(x) "data2.txt" u 1:2:(0.25) via a,b
Or you can do it completely within gnuplot without any intermediate file:
f(x)=a*x+b
fit f(x) "< awk '{print $1, $2} {print $3, $4} {print $5, $6}' data.txt" u 1:2:(0.25) via a,b
来源：https://stackoverflow.com/questions/23586904/fitting-a-function-with-multiple-data-sets-using-gnuplot