How to replace values?

How can I replace values? I've a matrix of 3653x337 Let's consider I've

• dates values
• 0101 0
• 0102 0
• 0103 0
• 0104 1
• 0105 0
• 0106 0
• 0107 0 ....

I need a function to find all these "1"'s in my matrix and to replace it for two days before and after I've a "1".

Thanks!

[Azzi Abdelmalek]

This is not clear

[Ugur]

sorry! I wish to copy in the 2 days before and after the "1" that I have. For example here we have 1 only for 4th January (0104) I want now Matlab to copy 1 to 0102,0103 and 0105, 0106.

[Cedric]

And why not to 0101 and 0107?

[the cyclist]

I think he means that if there is a 1 in the second column, put two more 1's before and two more after (all in the second column).

Answer 1

[the cyclist]

Here is a simple way that should be easy to understand. I am sure there are slicker ways, but maybe this will suit your purpose.

oldIndex = find(values==1);
newIndex = unique([oldIndex-2; oldIndex-1; oldIndex; oldIndex+1; oldIndex+2]);
values(newIndex) = 1;

[Azzi Abdelmalek]

newIndex = unique([oldIndex-2; oldIndex-1;oldIndex+1; oldIndex+2]);

without oldIndex

[Ugur]

it works very well!!!

Thanks!

[Jos (10584)]

This errors when values has 1's in the beginning or the end ... Moreover, you can skip unique.

Answer 2

[Jos (10584)]

Here's a one-liner:

values = [0 0 0 1 0 0 0 0 0 1 0 0 0 0 0 0 0 1]
values(max(min(bsxfun(@plus,reshape(find(values==1),[],1),-2:2),numel(values)),1))=1

or in more readable format:

values = [0 0 0 1 0 0 0 0 0 1 0 0 0 0 0 0 0 1]
oldIndex = find(values==1) 
newIndex = bsxfun(@plus, oldIndex(:), -2:2)
newIndex = max(newIndex,1)
newIndex = min(newIndex,numel(values)) 
values2 = values % work on a copy
values2(newIndex) = 1

Note that you do not need unique numbers for right-hand indexing

B = [0 0 0]
B([2 2 2 2 2 2]) = 1

[Ugur]

I've an error message saying that "undefined function 'nume1' for input arguments of type 'double'".

[Jos (10584)]

you should type numel with an lower case L instead of the digit 1 ...

[Ugur]

: )

thank you a lot!!!