use array elements as an index

Question

Suppose that we have the following array declaration in matrix

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

which looks in matlab as usual matrix form

a =

 1     2     3
 4     5     6
 7     8     9

I am interested how following code works

[a a(a) ]

here is given of course it's answer from a book

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

as I understood first a in bracket simply display original a, or number from 1 to 9, as a second case is use array elements as index into array, so it means that for example numbers

1   2  3
4   5  6
7   8   9

these are indexes for array a, first index a[1]=1,a{2]=2,a[3]=3 .... a[9]=9 is this right? But why does it print in transpose manner? Should not be like the original matrix? Thanks a lot.

DWilches · Accepted Answer · 2013-03-27 05:26:18Z

2

In this case the rows are traversed before the columns so a[2] = 4, a[3] = 7 and a[4] = 2

answered Mar 27, 2013 at 5:26

DWilches

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2 Comments

user466534 Over a year ago

so how can i distinguish when will be first traversed rows and when columns?

DWilches Over a year ago

That is the rule in Matlab. When you use only one index into a bidimensional matrix it will always traverse first the rows.

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