How can I set xticklabels to an array?

Hi,

I am trying to generate a plot and I need to set the x axis and y axis lables to some value I am calculating.

Initially I was hard coding them as strings but its not really convenient as every time I tune any parameter, I have to redo them. Is there a better way to do so?

noise = [0,1000,3000,5000,7000,9000,11000,13000];
snr=[];
for i=1:length(noise)
    snr = [snr,10*log10((1000/noise(i))^2)];
end
% Need to set xlim as the calculated values in snr. 

Currently I am doing something like this

p1 = plot(obj1(1,:)/30);
hold on;
p2 = plot(obj1(4,:)/30);
p3 = plot(obj1(5,:)/30);
p4 = plot(obj1(6,:)/30);
p5 = plot(baseline/30);

 phandles = [p1 p2 p3 p4];
 for h=1:length(phandles)
     set(phandles(h),'LineWidth',3, 'LineStyle', linestyles{h}, 'MarkerSize', myMarkerSize, 'Marker', markers{h});
 end

set(p5,'LineWidth',3, 'LineStyle', ':', 'MarkerSize', myMarkerSize,'Marker', 'x');
grid;

xlabel('SNR (dB)')
ylabel('PRR of ACK A');

ylim([0 1.1]);
xticklabels({'Inf','0','-9.54','-13.97','-16.90','-19.08','-20.82','-22.27'}) %need to use an array instead

leg = legend({'x4', 'x2.77', 'x2.04', 'x1','Baseline-A'},'Location','northeast');
leg.FontSize = 30;
title(leg,'Power Ratio (A:B)');
set(gca,'FontSize',myFontSize);

a = get(gca,'XTickLabel');  
set(gca,'XTickLabel',a,'fontsize',20,'FontWeight','bold') %changes the font size of axis lables

If someone can point me towards how I can use an array to set xticklabels or yticklabels then it would be really helpful.

Answer 1

[DGM]

The array given to xticklabels() doesn't have to be a cell array of chars. It can be

• a cell vector of chars
• a cell vector of mixed char vectors and numeric scalars
• a numeric vector

So if you can calculate those values, you could probably just use a numeric input instead of trying to convert to cellchar.

plot(1:10)
xticks(1:10)
xticklabels([Inf 2:10]) % numeric inf will be printed as "Inf"

[Raghav Rathi]

Thanks for the reply.

For the case I mentioned, doing

snr=[];
for i=1:length(noise)
    snr = [snr,floor(10*log10((1000/noise(i))^2))];
end
xticklabels(snr);

Is working but I have another case in which I need to xticklabels to be the following values.

x_tick = [0:-10:-120,,-150,-200];
% 0   -10   -20   -30   -40   -50   -60   -70   -80   -90  -100  -110  -120 -150  -200
xticklabels(x_tick);

But the resulting plot looks like this. I am not sure why the x axis is only stopping at -30.

[DGM]

You'll need to set xticks() as well.

Bear in mind that the labels set by xticklabel() are arbitrary. Without having xticks set as intended, there's nothing from the labels themselves that's being used to control how many ticks there are or where the ticks go.

[Raghav Rathi]

I understand what you are saying,

So I need to set xticks() first so that the plot can do the mapping according to the ticks and then label them using xticklabel() as i want.

My xticks are somethign like this

% Values to be plotted
obj2 = [
8 6 16 19 12 21 24 22 18 21 24 30 30 28 30
4 1 8 15 19 20 23 21 16 21 18 30 26 27 30
3 1 6 14 14 20 20 21 18 9 11 17 18 25 26
];

p1 = plot(obj2(1,:)/30);
hold on;
p2 = plot(obj2(2,:)/30);
p3 = plot(obj2(3,:)/30);


x_tick = [0:-10:-120,-150,-200];
%0   -10   -20   -30   -40   -50   -60   -70   -80   -90  -100  -110  -120  -150  -200

xticks(abs(x_tick)); %Value must be a numeric vector whose values increase.
xticklabels(x_tick); %label them as the original value 

Does this sound correct theoretically?

If so, then this is still giving me the same result as above.

Can you help me with understanding what am I doing wrong here?

[DGM]

Bear in mind that xticks corresponds to the xdata. In this case, that's implicitly the indices of obj2 (i.e. 1:15).

% Values to be plotted
obj2 = [
    8 6 16 19 12 21 24 22 18 21 24 30 30 28 30
    4 1 8 15 19 20 23 21 16 21 18 30 26 27 30
    3 1 6 14 14 20 20 21 18 9 11 17 18 25 26
    ];

figure
p1 = plot(obj2(1,:)/30); hold on;
p2 = plot(obj2(2,:)/30);
p3 = plot(obj2(3,:)/30);

x_tick_lab = [0:-10:-120,-150,-200];
xticks(1:15); %Value must be a numeric vector whose values increase.
xticklabels(x_tick_lab); %label them as the original value 

That said, I'm kind of confused with what you're trying to do with this relabeling. Using the labels alone to denote a nonlinear scale tends to be visually misleading, and I'm sure you can see how it requires a workflow that is prone to mistakes. If you're trying to force the axis direction to be reversed, you could accomplish that without needing to relabel everything.

% Values to be plotted
obj2 = [
    8 6 16 19 12 21 24 22 18 21 24 30 30 28 30
    4 1 8 15 19 20 23 21 16 21 18 30 26 27 30
    3 1 6 14 14 20 20 21 18 9 11 17 18 25 26
    ];
x = [0:-10:-120,-150,-200];

figure
p1 = plot(x,obj2(1,:)/30); hold on;
p2 = plot(x,obj2(2,:)/30);
p3 = plot(x,obj2(3,:)/30);

set(gca,'xdir','reverse') % if you want to flip the axis direction

Granted, I just let this throw the ticks wherever it wanted. If you do want all the ticks, you'd need to specify that, but the labels wouldn't need to be specified.

% Values to be plotted
obj2 = [
    8 6 16 19 12 21 24 22 18 21 24 30 30 28 30
    4 1 8 15 19 20 23 21 16 21 18 30 26 27 30
    3 1 6 14 14 20 20 21 18 9 11 17 18 25 26
    ];
x = [0:-10:-120,-150,-200];

figure
p1 = plot(x,obj2(1,:)/30); hold on;
p2 = plot(x,obj2(2,:)/30);
p3 = plot(x,obj2(3,:)/30);

xticks(fliplr(x))
set(gca,'xdir','reverse') % if you want to flip the axis direction

[Raghav Rathi]

Sorry for the confussion in my problem statement. The second approach you mentioned is what I was looking for. Thanks again.