Accessing the index of a matrix element inside the cell array

Hey all,

I have a small question in regarding the access of index of a matrix element inside the cell array.

A = {[1 2 3 4] [ 'Node1' 'Node2' 'Node3']};

Above is my cell array. Now I need to get the index of an element of matrix inside the cell array.

For an example if c = 3, just an example, c may be any number.

then I need it's index like A{1,1}(1,3)

Can anyone help me in this?

Thanks in advance

[Stephen23]

Note that square brackets are a concatenation operator, so your example

[ 'Node1' 'Node2' 'Node3']

is equivalent to:

'Node1Node2Node3'

Answer 1

[Guillaume]

First, a few recommendations.

• If you're using vectors use linear indexing instead of 2D indexing. I.e. X{1} instead of X{1, 1}.
• if n<=3 ... elseif n>3 ... end, if the if is false you're guaranteed that the elseif is true. Therefore the elseif is not needed, you can simply write if n<=3 ... else ... end. In general, you should always finish by an else, not an elseif.
• don't use the same variable name, particularly one as meaningless as c for storing to different things. In your code, c is used to store the index where plotnumber is found in the cell array, then to store plotnumber.
• Whenever you end writing the same lines of code with only small variations between them it's a clear indication that there must be a better way, such as indexing.

In particular, with that last point, we can rewrite your code as:

[f,T1, X] = Samplemodel_Instat('Measuring_Data.mat');
% X will be like this X = {[ 2 4] [ 'Oil'  'Air']};
%Now defines the constants that will be used for plots, as 5xN matrices (as there are 5 different possible plots)
Colours = [0.831372559070587 0.815686285495758 0.7843137383461;
           0.25 0.25 0.25;
           0.952941179275513 0.87058824300766 0.733333349227905;
           0.31 0.31 0.31;
           0.831372559070587 0.815686285495758 0.7843137383461];
LineWidths = [0.5; 4; 2; 2; 0.5];  %0.5 is default for plot
LineStyles = {'-'; '-.'; '-'; '-'; '-'};  %'-' is default for plot
Markers = {'none'; 'none'; 's'; 'none'; 'none'};  %'none' is default for plit
for plotnumber = 1:n
    whichmodel = find(X{1} == plotnumber,1);
    if ~isempty(whichmodel)
        if n <= 3
            plotstyle = 1;   %which row of Colours, LineWidths, etc.. to use
        else
            plotstyle = discretize(plotnumber, ceil((0:4)*n/4), 'IncludeEdge', 'right') + 1;
        end
        if ismember(plotstyle, [1 3])
            plotindices = (1:150:numel(f)) / 3600;
        else
            plotindices = (1:200:numel(f)) / 3600;
        end
        plot(f(indices), T1(plotnumber, indices), ...
             'Color', Colours(plotstyle, :), ...
             'LineWidth', LineWidths(plotstyle), ...
             'LineStyle', LineStyle{plotstyle}, ...
             'Marker', Markers{plotstule}, ...
             'MarkerFaceColor', [1 1 1]);
        legend(X{2}(whichmodel));  %index 2nd element of cell array
    end
end

[surendra kumar Aralapura mariyappa]

thank you so much

[surendra kumar Aralapura mariyappa]

@ Guillaume

I used your code, but it is showing below error.

Undefined function 'discretize' for input arguments of type 'double'.
Error in suri3 (line 20)
            plotstyle = discretize(plotnumber, ceil((0:4)*n/4), 'IncludeEdge', 'right') + 1;

I searched using which functionname,

It exist in the right dictionary.

C:\toolbox\matlab\datatypes\@categorical\discretize.m % categorical method

I am not surew what is going wrong!

Can you help me in this?

I am using both R2014a and R2017b both versions, In both versions it is showing this error. May I know when this function discretize was introduced?

I am using student version. is the above function available in the student version or not?

And also on community I read to function should be exactly in the working dictionary? what does it mean?

can you tell me, is there any way to fix it?

Thanks in advance

[Guillaume]

discretize requires R2015a or later. You shouldn't get an error in R2017b, but you'll definitively get one on R2014a.

On R2014a, replace that line by:

[~, plotstyle] = histc(plotnumber, ceil((0:4)*n/4) + eps(n));
plotstyle = plotstyle + 1;

Answer 2

[Soumya Sinha]

Hello Surendra,

Here in this case you have created a 1*2 Cell array in which first element is an array of numbers and the second one is the array of strings.

You can access the number 3 by writing the code

A{1,1}(3)

[surendra kumar Aralapura mariyappa]

@ Sinha,

I just copied only a part of my code here. My main motto is different. As you can see in my question, if c= 3, which means c will be user input in my code. my code is very big and also it takes too much time to explain everything here.

Here you can see,

A = {[ 2 4] [ 'Node2'  'Node4']};
for plotnumber = 1:n
    c = find(A{1,1} == plotnumber,1);
    if ~isempty(c)
        c = plotnumber;
end
end

Here Again I need to find the Index of this c or plotnumber which is there inside the cell array A.

I hope that now it is understandable.

Thanks in advance

[Guillaume]

@surendra,

Your code is working fine, so it's really not clear what problem you're having. It's not clear what you mean by the index of c (which is scalar).

[surendra kumar Aralapura mariyappa]

@ Guillaume,

' It's not clear what you mean by the index of c (which is scalar)'

Okay, I am going to put my code here. I already asked for the answer in the community, waiting for the answer yet. Again I am going to ask here also.

You can see in the below code. Accoding to the Values in the Cell array X{1,1} plot will be plotted. But I need to give legend to each plot everytime. So Here is the user input cell array

[f,T1, X] = Samplemodel_Instat('Measuring_Data.mat');
% X will be like this X = {[ 2 4] [ 'Oil'  'Air']};
for plotnumber = 1:n
    c = find(X{1,1} == plotnumber,1);
    if ~isempty(c)
        c = plotnumber;
        if n <= 3 
        plot(f(1:150:end)/3600,T1(c,1:150:end),'Color',[0.831372559070587 0.815686285495758 0.7843137383461]);
        elseif n > 3
            if c >= 1 && c <= ceil(n./4)
         plot(f(1:200:end)/3600,T1(c,1:200:end),'Color',[0.25 0.25 0.25],'LineWidth',4,'LineStyle','-.','MarkerFaceColor',[1 1 1],'Marker','none');
         %legend()
            elseif c > (ceil(n./4)) && c <=  ceil(n./2)
                plot(f(1:200:end)/3600,T1(c,1:200:end),'Color',[0.952941179275513 0.87058824300766 0.733333349227905],'LineWidth',2,'MarkerFaceColor',[1 1 1],'Marker','s');
                     %legend()
            elseif c > (ceil(n./2)) && c <= ceil(3*n./4)
                plot(f(1:200:end)/3600,T1(c,1:200:end),'Color',[0.31 0.31 0.31],'LineWidth',2,'LineStyle','-','Marker','d','MarkerFaceColor',[1 1 1]);
                   %legend()
            elseif c > (ceil(3*n./4)) &&  c <= n
                 plot(f(1:150:end)/3600,T1(c,1:150:end),'Color',[0.831372559070587 0.815686285495758 0.7843137383461]);
               %legend()
            end
        end
    end
end

So here According to the cell array, plot will be plotted, but I need to give the name to each plot using legend. For an example if c = 2, legend will be oil. like this I needed.

I thought of doing it in another way. But I got to know it is not possible.

The question is very simple, how to get the legend according to c. so here c is X{1,1} and legend is X{1,2}.

I hope that now at least it is understandable.

Thanks in advance