trailing string input must be double or native error

hi, i have a text file that i have attached. i am plotting the 4th column.but the curve has some disturbances. to smoothen the curve i used the average:

for i=2:250 a(i)=sum(y(i-1),y,y(i+1)) z(i)=a(i)/3 end

i am getting the following error: error using sum trailing string input must be "double" or "native". what is the errror?

thanks in advance.

regards, shiksha

[shiksha]

for i = 2:249 z(i) = sum(y(i-1:i+1))/3; end

how to display the answer z that i have obtained? i am just able to plot it.. and i want to plot the differential of z with time(5th column in text file), so i used: plot(diff(z)./diff(m(1:250,5)),'x') but i am getting an error : error using ==>rdivide matrix dimensions must agree..

the size of z is 1 249 the size of m(:,5) is 250 1 can u just tell me what is the error? please help..

regards, shiksha

[shiksha]

i got the answer. i just hd to transpose one input.

Answer 1

[Mischa Kim]

Shiksha, I assume your text file has 250 rows? If that's the case in the statement

a(i)=sum(y(i-1),y,y(i+1))

you are accessing for i=250 the 251 st element, y(i+1), which results in the error. Also, the middle term does not access a particular element. Finally, unless you need matrix a, you could simply do

 for i = 2:249 
    z(i) = sum(y(i-1:i+1))/3;
 end

[shiksha]

thanks. its working now.

[shiksha]

do u know how to apply low pass filter to smoothen the curve?

[shiksha]

how to display the answer z that i have obtained? i am just able to plot it.. and i want to plot the differential of z with time(5th column in text file), so i used: plot(diff(z)./diff(m(1:250,5)),'x') but i am getting an error : error using ==>rdivide matrix dimensions must agree..

can u just tell me what is the error? please help..

regards, shiksha