Using cellfun to extract specific rows from a cell array?

Hello,

I have a 1x6 cell array, 'Peaks':

Peaks = {199x4500} {192x4500} {167x4500} {171x1950} {157x1500} {191x1500}

I would like to create a new cell array, 'New_Peaks' using only 16 rows from each cell. The row numbers I want to choose are are in a 16X6 double array, 'Indices'.

Indices = 
2	1	1	1	4	1
16	23	7	72	133	24
44	30	19	15	13	63
41	15	28	9	18	58
35	26	31	3	15	4
8	49	39	19	53	32
11	72	40	96	29	64
14	39	55	73	111	84
153	33	57	129	12	71
70	116	63	92	75	60
144	104	95	94	68	83
137	137	97	108	77	74
91	155	107	140	120	97
36	40	119	49	144	56
80	64	127	105	43	59
160	94	145	66	149	49

I tried the following line:

New_peaks = cellfun(@(x) x(Indices), all_peaks, 'UniformOutput', false)

But the output is a 1x6 cell array consisting of 16x6 doubles.

The output I want is:

New_peaks = {16x4500} {16x4500} {16x4500} {16x1950} {16x1500} {16x1500}

Is cellfun able to extract the contents of a cell array in this way?

[the cyclist]

Can you upload the data, using the paperclip icon in the INSERT section of the toolbar? That makes it easier to see if code we try gives what you want.

[omidm]

Hi, sure, uploaded the 'peaks' and 'indices' variables.

[the cyclist]

Separate piece of advice: Don't name a variable "peaks", which shadows the name of a function. That can cause issues and confusion.

Answer 1

[Matt J]

New_peaks =cellfun(@(a,b) a(b,:), Peaks,num2cell(Indices,1)  ,'uni',0);

[omidm]

Thanks! This worked.

[omidm]

Hi Matt,

Do you have any advice on how I would write this line if my indices were stored in another cell array rather than a double array?

[Matt J]

Indices=num2cell(cell2mat(Indices),1)

New_peaks =cellfun(@(a,b) a(b,:), Peaks,Indices ,'uni',0);

[omidm]

Thanks Matt. Unfortunately, my indices are in a 1X6 cell aray because each column has different dimensions.

[848 X 1] [901 X 1] [870X 1] [295 X 1] [46X 1] [163 X 1]

Therefore, cell2mat won't let me concatenate into a double matrix.

I guess my overall goal is to use one 1X6 cell array (Indices) to index another 1X6 cell array (Peaks).

[Matt J]

In that case, you can just use Indices in its current form.

New_peaks =cellfun(@(a,b) a(b,:), Peaks,Indices ,'uni',0);

I would also encourage you to read the cellfun documentation to understand what this is doing.

[omidm]

Great, thanks!