replacing values in a cell array for matching values from another

Question

There is a cell array in MATLAB

B = 

    [ 1708]    [ 2392]    '+'
    [ 3394]    [ 3660]    '+'
    [ 5490]    [ 5743]    '+'
    [ 7555]    [ 7809]    '-'
    [ 9256]    [ 9509]    '-'
    [12878]    [15066]    '-'
    [16478]    [17458]    '-'

and another cell array

C =

[4]
[7]
[1]
[6]
[2]
[5]
[3]

I want to replace the values in C with the values in B{...,3} such that C becomes

C = 

    '-'
    '-'
    '+'
    '-'
    '+'
    '-'
    '+'

How can I do that in MATLAB? I currently did this but got error

>> C(C == 'x') = B
Undefined function 'eq' for input arguments of type 'cell'.

I don't understand your code sample. Why are you comparing to x? — Daniel
– Daniel, Commented Feb 26, 2014 at 18:45
It makes no sense to compare to the char 'x', at least following your problem description. — Daniel
– Daniel, Commented Feb 26, 2014 at 18:55

chappjc · Accepted Answer · 2014-02-26 20:43:00Z

3

Horizontal concatenation ([]) with comma-separated list cell array output ({:}) gives a direct way to index the appropriate rows in B:

Cnew = B([C{:}],3)

edited Feb 26, 2014 at 20:43

answered Feb 26, 2014 at 19:30

chappjc

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2 Comments

Floris Over a year ago

I like this approach.

chappjc Over a year ago

One-liners aren't very helpful without a little explanation... now for some links.

Floris · Accepted Answer · 2014-02-26 19:24:43Z

2

You could try

C = cellfun(@(x)B(x,3),C);

This addresses the problem you were seeing with C no longer being a cell array - note the subtle difference between B{} and B().

edited Feb 26, 2014 at 19:24

answered Feb 26, 2014 at 18:43

Floris

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5 Comments

chris Over a year ago

That made C a 7x1 char, I need to keep it as a Cell array

Divakar Over a year ago

Use NUM2CELL around it. It would be - C = num2cell(cellfun(@(x)B{x,3},C));

Stewie Griffin Over a year ago

@Divakar, please don't edit someone else's answer, even if you have a better suggestion. Leave a comment, and let the person who answered edit it if he/she feels like it. (You may edit to make it readable, typos, formatting etc., but not the content).

Divakar Over a year ago

@ Robert, I am still learning the etiquette of commenting here! Thanks @Floris.

Floris Over a year ago

@chris see my update. Replacing the {} with () fixed the problem you were seeing.

Daniel · Accepted Answer · 2014-02-26 18:54:03Z

1

Basic indexing, to get the elements of X in the order a=[1,3,2,4] use X(a). Indices are matrices, thus a conversion is needed, nothing else.

B(cell2mat(c),3)

answered Feb 26, 2014 at 18:54

Daniel

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