I have 20 values of lambda and 16 values of t and a matrix of size 15x16 how can I find exp(-lambda*t)*v

lambda=linspace(.1,1.99,20);
t=linspace(0,1,16);

[dpb]

I did it for you this time, but please format the code to be legible--note that two blanks before the first line of a paragraph starts a code section. Look at the format for the posting in the Edit window and compare what happens in the Preview window if you remove one of those, etc., ...

Answer 1

[Star Strider]

I have no idea what data you are analysing or simulating, so I have no idea what your constraints might be. One option would be to simply specify ‘lambda’ to be 16 rather than 20 values over the same span:

lambda=linspace(.1,1.99,16);

A second option is to extrapolate ‘v’ to also be (20x15):

lv = lambda(1:15);
ve = interp1(lv, v, lambda, 'pchip', 'extrap');
eltv = exp(-lambda'*t).*ve;

figure(2)
plot(t, eltv)
grid

This assumes that ‘v’ is in some way related to ‘lambda’, so the extrapolation takes the first 15 values of ‘lambda’ and uses the full ‘lambda’ vector to extrapolate ‘v’ to ‘ve’. Since ‘lambda’ is linear, it is as good a choice as any. Choose the extrapolation method that is most appropriate for your data among the available options. (I chose 'pchip' for no particular reason. You must choose a method if you want to extrapolate.)

[Fatin]

Thank you for your answer , and sorry if my question was not clear . you give me a good idea . I can't change size of lambda , they must be 20 values , but I can change size of t to be 1x20 vector , and want to make my matrix v to be 15x20. So I had tried to make the following code butt it still gives me error

 lambda=linspace(.1,1.99,20);

   t=linspace(0,1,16);
   t1 = linspace(0,1,20);
   ve = interp1(t,v,t1, 'linear');
   eltv = exp(-lambda'*t1).*ve

[Star Strider]

My pleasure!

Your ‘v’ matrix has to be the same size as: exp(-lambda'*t1). In your new code, all your matrices have to be (20x20). Since I am not certain what you want to do, I will leave extrapolating ‘v’ (as ‘ve’) to you. Note that ‘t’ has to have the same row size as ‘v’. Just now, ‘t’ is (1x16) and ‘v’ is (15x16), so you have to define ‘t’ as having 15 elements (either as a row or column vector) for interp1 to work here.

You also have to change this line to include the 'extrap' option:

ve = interp1(t,v,t1, 'linear','extrap');

That way you can ‘stretch’ ‘v’ to the dimension you want. If you do not specify 'extrap', and if ‘t1’ is longer than ‘t’, the interp1 function will throw an error.

[Fatin]

Thanks again , I will try that.

[Star Strider]

My pleasure!