if loop not executing

i have dataset of 80 numbers=[1:1:80]

now i want to take first 8 values ,multiply each value by 2 and divide each by 2,so i will have 8 values each for multiplication and division,and then want to find average for that multilaction values and division values,same way i want to perform for those 80 values from 1st 8,2nd 8,3rd 8........10th8 please help..

i tried the folowing but it is not executing

z=0
if index<=8 +z
Sum=index+2
mul=index.*2
end
avg=mean(Sum)
avg=mean(mul)
z=z+1

i get answer as z=0

z=1

please help

[Fangjun Jiang]

Where is the for-loop and what is your variable index?

[kash]

Sorry fangjun it is "if loop"

index is my dataset=[1:1:80]

[Walter Roberson]

There is no such thing as an "if loop". There is "for loop" and "while loop" and "if statement", but not "if loop".

[kash]

ok walter it is "if statement"

Answer 1

[bym]

use reshape to organize your values into 8 rows and 10 columns. You can then use mean() after your multiplications & divisions.

x = 1:80;
x = reshape(x,8,[]);
...

Answer 2

[Image Analyst]

I answered this where you first asked it http://www.mathworks.com/matlabcentral/answers/24562-selecting-an-image-from-folder My answer of using conv was also suggested by someone else in your third thread for this http://www.mathworks.com/matlabcentral/answers/24848-performing-certain-operation-from-a-set-a-certain-set-of-values

Can you explain in words what you actually want to do? Is it a running average? Or something else?

[kash]

Actually i need in final of 10 average values in sum and multiplication,and i need each

foe example

the sum of first 8 values must be stored in an variable and so on till end(last 8 values)and same for multiplication,and average also

i dont know what u mean by running average

[Image Analyst]

For example, output(1) = mean(input(1):input(8)), output(2) = mean(input(2):input(9)) and so on, moving over one element at a time.

Answer 3

[Fangjun Jiang]

if-else statement won't do any loop.

I assume this is an exercise. You almost need to re-work on the code completely.

"multiply each value by 2 and divide each by 2", but you are adding it by 2.

It's meaningless to do mean() on a scalar.

I suggest you go to the MATLAB document, MATLAB->Getting Started.