merging elements into a single cell array

I have a 366x1 cell array named B. i would like to copy each row into another cell array like 2nd and 3rd value of 1st row will be merged with 2nd and 3rd value of 2nd row into a new cell array (as both index is 8). Similarly 2nd and 3rd value of 3rd row will be merged with 2nd and 3rd value of 4th row into a new cell of the same cell array (as both index is 17) and so on.

[James Tursa]

Do all of the rows always have exactly three elements?

[Satarupa Khamaru]

Hi James,thanks a lot for your quick assistance. Yes, all rows have exactly three elements.

[Image Analyst]

Can you save B to a .mat file and upload it so we can try to work with it?

Answer 1

[James Tursa]

Does this do what you want?

C = cellfun(@(c)c(2:end),B,'uni',false);
v = cellfun(@(x)x(1),B);
u = unique(v);
result = arrayfun(@(x)[u(x),C{v==u(x)}],1:numel(u),'uni',false)';

[Satarupa Khamaru]

the above code is not giving the desired result. Here I have uploaded B as a .mat file and also I uploaded result as .mat file, this is the format I want exactly. Here in stead of [2,24;595,67], the value should be 1st row of cell B and 2nd row of cell B together separated by semicolon i.e. [-0.7904,0.9728;1.463,0.8094].

[James Tursa]

What about this?

M = cell2mat(B);
v = M(:,1);
u = unique(v);
result = arrayfun(@(x)M(v==u(x),2:end),1:numel(u),'uni',false);

[Satarupa Khamaru]

Thank you very much James. This is exactly what I was looking for and was breaking my head since long time. I am very new to matlab. Your quick assistance with this is much appreciated. Would you mind explaining the 'arrayfun' syntax? it would be a great help for me. thanks

[James Tursa]

arrayfun( ) operates on each element of an array. In this case, it is the array formed by 1:numel(u). For each of these values 1, 2, 3, ..., numel(u), an output is generated by the first argument:

@(x)M(v==u(x),2:end)

This is a function handle, which picks off the rows of M that match u(x) and the 2nd through last columns of these rows. So in your example above, the 8 in the first column appears in the first two rows. So this function handle, when evaluated with a 1 input, generates this result:

M(v==u(1),2:end)

Since u(1) is 8, this is equivalent to:

M(v==8,2:end)

I.e., this picks off the rows of M where the first column contains an 8. The 2:end picks off all of the columns except the first column.

For the next element of the result, a value of 2 is used as input to the function handle, so you get this:

M(v==u(2),2:end)

which gives this

M(v==17,2:end)

Etc.

Finally, the ...,'uni',false,... stuff is simply to tell arrayfun( ) to put the results into a cell array.

[Satarupa Khamaru]

Thanks again for such a detail explanation, it helps a lot. thanks