How do I add horizontal lines and text to a wcoherence plot?

Hi everyone,

I'm trying to draw a horizontal line and add some text to a wcoherence plot (because I'd rather do it in Matlab than in Illustrator afterwards). Using the first example in https://www.mathworks.com/help/wavelet/ref/wcoherence.html

figure

rng default;

t = 0:0.001:2;

x = cos(2*pi*10*t).*(t>=0.5 & t<1.1)+ ...

cos(2*pi*50*t).*(t>= 0.2 & t< 1.4)+0.25*randn(size(t));

y = sin(2*pi*10*t).*(t>=0.6 & t<1.2)+...

sin(2*pi*50*t).*(t>= 0.4 & t<1.6)+ 0.35*randn(size(t));

wcoherence(x,y,seconds(0.001));

How would I add a horizontal white line at 0.2 seconds and the text "0.2 seconds" right above it? I know it's possible because the following line in wcoherence (723) plots the cone of influence:

plot(ax,t,log2(coi),'w--','linewidth',2)

I've tried pasting the following code into the wcoherence function, right after the cone of influence plot ^, but no matter what I do, the line and text don't show up.

linex = [min(t) max(t)];

liney = [0.2 0.2];

plot (AX, linex, log2(liney), 'w-', 'linewidth', 1);

text (min(t)+0.1, log2(0.2+0.05), '0.2 seconds')

I suspect it's something with the 'layer' of the plot or that I'm pasting it in the wrong part of wcoherence or that I'm misunderstanding the conversions between frequencies and periods and log scaling, but I'm stumped.

Thanks so much for your help!

Answer 1

[Sakshay]

Hello Bryce,

As per my understanding, you are trying to plot a horizontal line, on an already generated wcoherence plot.

To retain the current plot in MATLAB, we have to use the "hold on" function. "hold on" retains plots in the current axes so that new plots added to the axes do not delete existing plots. For your case the script would look like:

figure;
rng default;
t = 0:0.001:2;
x = cos(2*pi*10*t).*(t>=0.5 & t<1.1)+ ...
cos(2*pi*50*t).*(t>= 0.2 & t< 1.4)+0.25*randn(size(t));
y = sin(2*pi*10*t).*(t>=0.6 & t<1.2)+...
sin(2*pi*50*t).*(t>= 0.4 & t<1.6)+ 0.35*randn(size(t));
wcoherence(x,y,seconds(0.001));

% Hold the previous plot to generate the next plots over it
hold on
linex = [min(t) max(t)];
liney = [0.2 0.2];
plot (linex, log2(liney), 'w-', 'linewidth', 1);
text (min(t)+0.1, log2(0.2+0.05), '0.2 seconds');

You can refer to the following documentation on "hold" for more information:

Retain current plot when adding new plots - MATLAB hold (mathworks.com)

[Bryce Mitsunaga]

Hi Sakshay,

Sorry for the super slow reply, but ...yup, that was it, thank you so much! I thought the

hold(AX,'on');

around line 720 would do it, but it makes sense that you'd need a separate hold for subsequent plots at the end / over it.