it says it cant plot because my vectors aren't the same size but they are

yvec=[6.67 17.33 42.67 37.33 30.10 29.31 28.74];
xvec=[0 6 10 13 17 20 28];
xvar=0:.001:28;
yvar=P_N(xvec,yvec,xvar);
plot(xvar,yvar,xvec,yvec,'r*')

trying to run this code but it says

Error using plot

Vectors must be the same length. anyone know how to fix this?

Answer 1

[Torsten]

Check whether size(yvar) equals size(xvar).

I think this cannot be true because the following code works:

yvec=[6.67 17.33 42.67 37.33 30.10 29.31 28.74];
xvec=[0 6 10 13 17 20 28];
xvar=0:.001:28;
%yvar=P_N(xvec,yvec,xvar);
yvar = rand(size(xvar));
plot(xvar,yvar,xvec,yvec,'r*')

[allison]

so its wokring on your end?P_N is supposed to do the interpolation of it maybe its my code for these causing the error it keeps saying

RAN

Error using plot

Vectors must be the same length.

Error in

RAN (line 6)

plot(xvar,yvar,xvec,yvec,'r*')

function [out] = P_N(xvar,xvec,yvec)
%xvar is x variable value where we want to evaluate K_N_i(xvar)
%xvec is a vector of x coordinates from data points to be interpolated
%yvec is a vector of y coordinates from the data points to be interpolated
N=length(xvec); %how many data points do we have
out=0;
for index= 1:N
    out=out+yvec(index)*L_N_i(xvar,xvec,index);
end


    function [out] = L_N_i(xvar, xvec,ind4one)
        %xvar is x variable value where we want to evaluate K_N_i(xvar)
        %xvec is a vector of x coordinates from data points to be interpolated
        %ind4one is the index of the xvec value where  L_N_i will be equal to 1
        N=length(xvec); %this is the number of x coordinates
        num=1; %intializing numerator of L_N_i
        den=1; %intializing DENOMINATOR of L_N_i
        for index=1:N
            if index~=ind4one
                num=num.*(xvar-xvec(index));
                den=den*(xvec(ind4one)-xvec(index));
            end
        end
        out=num/den;
    end

[Torsten]

You call P_N as

yvar=P_N(xvec,yvec,xvar);

and the function is given as

function [out] = P_N(xvar,xvec,yvec)

Do you see that the inputs in the call to P_N are in the wrong order ?

[allison]

awesome yes that part is now working but when i do maxerror=max(abs(yactual-yvar)) it gives an erorr