Issue with DisplayName plot function in a loop

Hello all,

I am having an issue when trying to plot the display for specific vectors in a loop. Here is my code:

clf;
cc = jet(32);
for i=1:31
    check_NaN=~isnan(CN0_Plot_GPA_L1CA4(i,:));
    val_index=find(check_NaN);
    if ~isempty(val_index)
        p(i)=plot(Time(1:N_Packet)-fix(Time(1)),CN0_Plot_GPA_L1CA4(i,:),'color',cc(i,:), 'marker','+','DisplayName',['SV=' num2str(i)]);
        hold on
    end
end
legend(gca,'show')
grid on;
datetick('x','HH:MM');
xlabel(datestr(fix(Time(1))));
ylabel('CN0(dBHz)');
title('GPS CN0 for L1CA modulation ');

With this code I am getting a plot with all indexes i plotted.

Now, when I am doing a very similar algorithm but this time removing the abscissa in the plot (no more Time(1:N_Packet) in the plot) it is working as expected:

clf;
cc = jet(32);
for i=1:31
    check_NaN=~isnan(CN0_Plot_GPS_L1CA4(i,:));
    val_index=find(check_NaN);
    if ~isempty(val_index)
                             %
                             p(i)=plot(CN0_Plot_GPS_L1CA4(i,:),'color',cc(i,:), 'marker','+','DisplayName',['SV=' num2str(i)]);
                             %
        hold on
                             %
    end
end
legend(gca,'show')
grid on;
ylabel('CN0(dBHz)');
title('GPS CN0 for L1CA4 modulation ');

Any idea on how to solve this will be much welcome!

Best regards

[Walter Roberson]

I predict that N_Packet is not the same as the number of columns in CN0_Plot_GPS_L1CA4 .

In particular I predict that N_Packet is 2.

[Franck Borde]

Dear Walter,

I beleive that both my vectors Time and CN0_XXX have consistent size:

>> size(Time)

ans =

1 1935

>> size(CN0_Plot_GPA_L1CA4)

ans =

31 1935

What is puzzling is that this used to work on previous matlab version.

For some weird reasons it does not consider the IF statement when I am adding the Time vector in the plot.

Best regards,

Franck

[Walter Roberson]

you do not plot all of Time, you only plot N_Packet out of Time.

[Franck Borde]

Many thanks Walter for your hint!!!....indeed there was a mismatch in the dimension of my Time matrix.

Best regards,

Franck

[Image Analyst]

Are you SURE that worked with a prior version? The very same code? It seems like that would have thrown an error with any version. Just wondering...

Answer 1

[Image Analyst]

I don't see DisplayName as one of the options in R2018b. Is it one in your version?

What are you trying to do? Put a title on the plot? If so, try this:

p(i) = plot(CN0_Plot_GPS_L1CA4(i,:),'color',cc(i,:), 'marker','+');
caption = sprintf('SV = %d', i);
title(caption, 'FontSize', 20);
legends{i} = caption;
drawnow;

That should alter the title above the plot as you're plotting it.

If you also want to display a legend, do this after the loop

legend(legends, 'Location', 'north');

[Walter Roberson]

Image Analyst:

https://www.mathworks.com/help/matlab/ref/plot.html#description

plot(___,Name,Value)specifies line properties using one or more Name,Valuepair arguments. For a list of properties, see Line Properties. Use this option with any of the input argument combinations in the previous syntaxes. Name-value pair settings apply to all the lines plotted.

Then under Line Properties,

https://www.mathworks.com/help/matlab/ref/matlab.graphics.chart.primitive.line-properties.html#bubwqbv-1_sep_shared-DisplayName

DisplayName— Legend label

''(default) | character vector| string scalar

Legend label, specified as a character vector or string scalar. The legend does not display until you call the legendcommand. If you do not specify the text, then legendsets the label using the form'dataN'.

So, Yes, it is an option in your R2018b.

Answer 2

[Franck Borde]

Thanks Image Analyst for helping out!

I am using version R2018a. DisplayName works when the plot has only one variable but when I am adding the absciss then it is starting to mess around.

Proper Plot (limited number of SV's):

Plot when adding the absciss: