What does M([1:1 2:3], [1:0 2:3]) mean?

Hi,

Using a square matrix as an example:

>> M = [1 2 3; 4 5 6; 7 8 9]
M =

     1     2     3
     4     5     6
     7     8     9

I don't understand what does M([1:1 2:3], [1:0 2:3]) do to give the following answer?

>> select = M([1:1 2:3], [1:0 2:3])
select =

     2     3
     5     6
     8     9
     

Answer 1

[Arthur Roué]

This

select = M([1:1 2:3], [1:0 2:3])  

is awfully written, it means

select = M(1:3, [2 3])     

select is the lines 1 to 3 of M and colum 2 and 3

Answer 2

[Star Strider]

It is easier to understand if the values are calculated:

row_ref = [1:1 2:3] 
col_ref = [1:0 2:3]

produce:

row_ref =
     1     2     3

col_ref =
     2     3

Note that (1:0) produces:

1×0 empty double row vector

so it is actually redundant here.

.

Answer 3

[Fangjun Jiang]

First, run this line by line in Command Window to figure out what it does

1:5
1:0.5:3
5:-1:1

Then understand that [1:1 2:3] is the same as [1 2 3], [1:0 2:3] is the same as [2 3]

Thus the outcome is the [1 2 3] row and [2 3] column of matrix M