Filter contents of a table

The following contents are stored in a table, in variable 'tbl',

        Multico                     value
     ______________
    {'1'}    {'2'}                    1
    {'2'}    {'3'}                    2
    {'3'}    {'4'}                    1
    {'4'}    {'5'}                    2

I would like to do the following,

variable = 2,

If the variable is present in tbl.Multico, I would like to retain only those rows and delete the remining rows.

Example,

        Multico                     value
     ______________
    {'1'}    {'2'}                    1
    {'2'}    {'3'}                    2

Also, if variable is present in column 2 of Multico, the value in column 2 of tbl will remain unchanged. If the variable is

in column 1 of Multico the sign of the value in column2 of tbl will change.

Th expected output is,

        Multico                     value
     ______________
    {'1'}    {'2'}                    1
    {'2'}    {'3'}                    -2

I'd like to ask for suggstions on how this can be done.

Is there a function similar to python's groupby for filtering contents of a table?

Answer 1

[Guillaume]

Any reason why Multico is a cell array? If all the cells are just scalar, then it's a waste of memory and complicates the code for no good reason.

So first step, convert that cell array into a 2 column matrix:

yourtable.Multico = cell2mat(yourtable.Multico);

Your filtering is then trivially done:

serchval = 2;
newtable = yourtable(any(yourtable.Multico == searchval, 2), :)

If you then want to change the sign of value when searchval is in first column of Multico:

tochange = newtable.Multico(1, :) == searchval;
newtable.value(tochange) = -newtable.value(tochange)

[Deepa Maheshvare]

Many thanks for the response.

Any reason why Multico is a cell array?`

Yes, the table has ben created in the following way.

t = 1:4;
h = 2:5;
G = graph(t,h);

I've tried to name the nodes of the graph,

G.Nodes.Name = cellstr(string(1:height(G.Nodes))');
tbl = G.Edges

Gives the above table.

cell2mat(tbl.Multico) gives

  4×2 char array

    '12'
    '23'
    '34'
    '45'

[Guillaume]

Oh! I completely overlooked that you were storing char vectors and not numbers in Multico.

However, I must ask why? Why don't you stick with numeric node numbers instead of naming them?

Anyway, if you stick with a cell array of char vectors, then it's not much more complicated, just replace the == by a call to strcmp:

%no longer converting cell array to matrix since it contains char vectors.
serchval = '2';
newtable = yourtable(any(strcmp(yourtable.Multico, searchval), 2), :)

tochange = strcmp(newtable.Multico(1, :), searchval);
newtable.value(tochange) = -newtable.value(tochange)

[Deepa Maheshvare]

Thanks a lot. However, I get the following error.

The logical indices contain a true value outside of the array bounds.

Is it because we are trying to index with [0 1] stored in tochange (newtable.value(tochange))?

Answering you question,

Why don't you stick with numeric node numbers instead of naming them?

I want to access the nodes for deleting and adding edges. I am not sure how to access the nodes without names.

[Deepa Maheshvare]

It works!!