Assigning legend in for-loop Matlab

Question

I have tried giving the legend in the loop but it overwrites the previously written legend, how can insert them either in if statement or either in the for loop. Confused

    clear;
        vin=10
 for m=1:1:14;  

        vin=vin+10
    for i=1:1:27
        Wa_Ac = PVinv.CoreSizeModel();
        PVinv.CoreSelect(Wa_Ac,i);   
        loss_ind_core= PVinv.InductorLossModel(PVinv.m_L_Selected);

        if(i==1)
        p=plot(vin,loss_ind_core,'--gs');
        hold on
        end
        if(i==2)
        p=plot(vin,loss_ind_core,'--rs');
        end %...till i=27

        legend(obj.m_Core_List(i).name);
        xlim([10e3 90e3])
        set(gca,'XTickLabel',{'10';'20';'30';'40';'50';'60';'70';'80';'90'})
        grid on
        xlabel('Vin');
        ylabel('Power loss');
    end
 end

The called function

function obj = CoreSelect(obj, WaAc)
             obj.m_Core_Available= obj.m_Core_List(i);
            obj.m_L_Selected.m_Core = obj.m_Core_Available;

end 

Solution 1

Create a cell array to hold the legend names. Before the for loop define something like

legend_names = cell(1,27 * 14);

Then, during the loop fill the cell in:

legend_names{27*(m-1)+i} = obj.m_Core_List(i).name;

After the end set the legend:

legend(legend_names);

I might have misunderstood the indices (m vs i) and how they relate to the names, but the point is that you can pass a cell array to the legend function to create the legend at one time.

An example is:

>> legend_names=cell(1,2);
>> legend_names{1} = 'str';
>> legend_names{2} = 'str2';
>> plot(0:4,0:4)
>> hold on
>> plot(1:5,0:4)
>> legend(legend_names)

which would yield

Solution 2

Instead of collecting the legend string, you can just set the DisplayName-property in your plot commands. Also, you can collect the linespec arguments in a cell array to avoid code duplication, i.e.

linespec = {'--gs','--rs',... %# etc

(...) 

for i=1:1:27
        Wa_Ac = PVinv.CoreSizeModel();
        PVinv.CoreSelect(Wa_Ac,i);   
        loss_ind_core= PVinv.InductorLossModel(PVinv.m_L_Selected);


        p=plot(vin,loss_ind_core,linespec{i},'DisplayName',obj.m_Core_List(i).name);

end        

legend('show')

Solution 3

When faced with this situation, each time through the loop I add the legend string to a cell array of strings, e.g.

legstr{i} = obj.m_Core_List(i).name; 

and then display the legend once, after the end of the loop:

legend(legstr);

Comments

[mirage]

Error:Cell array argument must be a cell array of strings. Actually i has to loop 27 times for every m value. –

[user2032201]

@Khalid - you can use a string matrix instead of a cell (see weizmann.ac.il/matlab/techdoc/ref/legend.html for legend documentation)

[Taylor Southwick]

@Khalid where is the error coming in? I've edited it for 27 times for every m value

[mirage]

Used the logic but it turned out to be the same problem in the end, it rewrites on the previous legend values

[mirage]

The error was at the point when legend command is executed. Legend was not accepting the cell characters as its arguments

[mirage]

It worked out, i was using the if statements to do it..But as I moved my ifelse statements outside the for loop things worked out

[Taylor Southwick]

@Khalid Make sure you are assigning strings to the cell. It sounds like your cell array is not composed of strings.

[Bernhard]

For future reader: the example works perfectly for me in 2013b.