How to reference previous value in an array without a for loop?

Hi,

I have a for loop set up following a similar structure to this:

for i=2:size(data,1)
        data.Var3(i)=interp1(ref_data.x,ref_data.y,data.Var2(i))-interp1(ref_data.x,ref_data.y,data.Var2(i-1));
end

Where I use a reference table to interpolate a certain x value from my current data to obtain a corresponding y value, that is done twice per row.

It works, but the data table I'm using has 300,000 rows, so the run time of this loop alone is just under 3 mins in my case (data.Var3 is not being resized after every iteration in the loop).

Doing this operation this way simply takes too long, is there any way you can think of in which I can carry out the operation inside the for loop, without actually putting it inside a loop?

Any help is appreciated,

Thanks!

Answer 1

[Wan Ji]

use i=2:size(data,1); data.Var3(i)=interp1(ref_data.x,ref_data.y,data.Var2(i))-interp1(ref_data.x,ref_data.y,data.Var2(i-1));

[HWIK]

It was that easy... Thanks!

[Wan Ji]

my pleasure, :)