How to replace all zeros in a matrix with a vector from 1 to 9 in the order of ascending indices?

I have a matrix x

x =

     0     4     9     9    -4     0
     4     0    -3    -3    -1     0
     0     0     9     9     3    -2
     0     0     5     5    10     0
    -3     9    -4    -4    10     9
     0     0    -1     8     5     0

How can I replace all zeros with values 1 to 9 in the order of ascending indices?

[Jonas]

what do you mean with ascending indices? rowwiae, columnwise or sum of row and column number?

[Hearthy Tampol]

columnwise

[Image Analyst]

So why didn't my answer below work for you? It does it columnwise. Please show what you need as the output so I can adjust my code below. Also, is this homework?

[Hearthy Tampol]

Yes this is homework. I now realized where I lost it haha, there are elements that I incorrectly typed, my bad. But, thanks for the code, I was able to manipulate it to get the right answer I need. Thanks!!

Answer 1

[Image Analyst]

Try this. The replacements are in "column-major" order, since that's how MATLAB does things.

x = [
	0     4     9     9    -4     0
	4     0    -3    -3    -1     0
	0     0     9     9     3    -2
	0     0     5     5    10     0
	-3     9    -4    -4    10     9
	0     0    -1     8     5     0]

zeroMap = x == 0
numZeros = sum(zeroMap(:))
x(zeroMap) = 1 : numZeros

----------------------------------------------------------------------------------

x =

0 4 9 9 -4 0

4 0 -3 -3 -1 0

0 0 9 9 3 -2

0 0 5 5 10 0

-3 9 -4 -4 10 9

0 0 -1 8 5 0

zeroMap =

6×6 logical array

1 0 0 0 0 1

0 1 0 0 0 1

1 1 0 0 0 0

1 1 0 0 0 1

0 0 0 0 0 0

1 1 0 0 0 1

numZeros =

12

x =

1 4 9 9 -4 9

4 5 -3 -3 -1 10

2 6 9 9 3 -2

3 7 5 5 10 11

-3 9 -4 -4 10 9

4 8 -1 8 5 12

If, instead of 1-12, you want to go from 1-9 and then from 1-3, you can do this:

x = [
	0     4     9     9    -4     0
	4     0    -3    -3    -1     0
	0     0     9     9     3    -2
	0     0     5     5    10     0
	-3     9    -4    -4    10     9
	0     0    -1     8     5     0]

zeroMap = x == 0
numZeros = sum(zeroMap(:))
v = rem(0 : numZeros-1, 9) + 1
x(zeroMap) = v

v =

1 2 3 4 5 6 7 8 9 1 2 3

x =

1 4 9 9 -4 9

4 5 -3 -3 -1 1

2 6 9 9 3 -2

3 7 5 5 10 2

-3 9 -4 -4 10 9

4 8 -1 8 5 3

[Hearthy Tampol]

could you please sort it as a group in descending order of elements in column 6 because I am not getting the same answer as yours, I want to check where I lost it

[Image Analyst]

Not sure what good that would do, but you can use sortrows() to do what you asked for.

sortedx = sortrows(x, 6, 'descend'); % Sort by values in column 6.

[Hearthy Tampol]

thanks! That's what I really need, I just need to change some elements I incorrectly typed haha

[Image Analyst]

You're welcome. (Thanks for Accepting the answer to award reputation points.)

Tip: Did you know that you can click the double-page icon in the upper right corner of code sections to copy the code into the clipboard, then you can paste it into MATLAB editor window from the clipboard.