How to subtract the elements of an array

Hello,

I am coding an .m file in MATLAB R2018a. The code I have (partial) is:

nt=[8,17,22,25]'

for i=1:3
    grad(i)=nt(i+1)-nt(i)
end
sumgrad=sum(grad)

As you can see, I am trying to subtract the 2nd element of the array is subtracted to the 1st and place it on the index 1 of the array grad(i). . Then, the 3rd element of the array is subtracted to the 2nd and place it on the index 2 of the array grad(i). By last, the 4th element of the array to the 3rd and place it on the index 3 of the array grad(i)

Then, all the elements of the array grad(i) are sum into the variable sumgrad.

I am getting this error:

Error: Index exceeds array bounds.

I am quite sure there is a better way of coding this. Could someone help me?

Best regards,

Hugo

Answer 1

[Ameer Hamza]

Although your code seems correct and the error shouldn't occur, you can directly use diff() function and avoid the for-loop

nt=[8,17,22,25]';
grad = diff(nt);
sumgrad=sum(grad)

[Matt J]

Even easier:

sumgrad=nt(end)-nt(1)

Answer 2

[Matt J]

At which line does the error occur?The only thing I can think of is that you accidentally have a variable called "sum" previously defined in your workspace, e.g.,

sum=0;

nt=[8,17,22,25]'

for i=1:3
    grad(i)=nt(i+1)-nt(i)
end
sumgrad=sum(grad)

Index exceeds the number of array elements (1).

Error in test (line 11)
sumgrad=sum(grad);