how to multiply a number to matrix?

Hello everyone,

I have a matrix 180X360X1332 (Latitude X Longitude X Time). I want to multiply 30 at every fourth number of third demension (e.g., 1,5,9,13......1332)

I have tried this for vector data:

Y = 30*(1:4:1332);

How can I do this for matrix data?

Thanks

[Bruno Luong]

"a number 30 in time demension at interval of 4"

Not sure someone can understand this.

[Aarti Soni]

@Bruno Luong I have updated my question. Hope this is clear now.

[Bruno Luong]

If that is the case, see @vishweshwar samba answer

Answer 1

[vishweshwar samba]

I assume that the matrix 180X360X1332 (Latitude X Longitude X Time) is a multidimentional array and you want to multiply a value of 30 to (Latitude X Longitude) in the interval of 4 wrt Time.

% By using the below for loop, created a matrix 'A' of dimension 180x360x1332 (Latitude X Longitude X Time)
for i = 1:1332
    A(:,:,i) = ones(180,360);
end

% Now multiply a number 30 in time dimension at interval of 4(1:4:1332)
A(:,:,1:4:1332) = A(:,:,1:4:1332)*30;

[Aarti Soni]

@vishweshwar samba @Bruno Luong I have tried this but not working

for i = 1:1332,
        x = data(:,:,i);
        y = x(:,:,1:4:1332)*30; 
        z(:,:,i) = y;
end;

[Aarti Soni]

here the third dimension is rainfall data for 1332, so I want to multiply a value of 30 to rainfall data.

[Bruno Luong]

Remove the for-loop, just

data(:,:,1:4:end) = data(:,:,1:4:end)*30;

[vishweshwar samba]

I dont understand why you are using for loop. Instead replace your code with the code mentioned below.

data(:,:,1:4:1332) = data(:,:,1:4:1332)*30;

[Bruno Luong]

If you prefer for-loop

z = data;
for i = 1:4:size(z,3)
    z(:,:,i) = z(:,:,i)*30;
end

[Aarti Soni]

Thanks @Bruno Luong it works

[Aarti Soni]

Hi @Bruno Luong

I have one more question in this regard, suppose, I have a time series (1x48) and I want to extract values at particular interval. Means, I want to creat a new time series which will have only 12 values. e.g., 1,5,9,13,17, 21, 25, 29, 33, 37, 41, 45

How can I do this?

Thanks

[Bruno Luong]

@Aarti Soni I suggest you to create a new thread and better description. Someone else can answer to you.