How to link both y-axes in a yyaxis subplot? - matlab

I'm trying to individually link both y-axes in an yyaxis subplot. So far I'm only linking the right y-axes in the given code by calling linkaxes(g), where g are the axes handles. How can I also get the left y-axes linked to one another?
Thanks.
g(1) = subplot(2,1,1);
hold on;
yyaxis left;
plot(rand(10,1));
yyaxis right;
plot(2*rand(10,1));
hold off;
g(2) = subplot(2,1,2);
hold on;
yyaxis left;
plot(2*rand(10,1));
yyaxis right;
linkaxes(g);
plot(rand(10,1));
hold off;

An Axes object has the read-only property YAxisLocation that is set upon every call to yyaxis and remembers the last axis that was in use. When you type linkaxes(g) it simply takes the right axis because that the last one you set. To see that you can run this code for the first axes:
g(1) = subplot(2,1,1);
hold on;
yyaxis right;
plot(2*rand(10,1));
yyaxis left;
plot(rand(10,1));
hold off;
and see how this time the left top axis is linked to the right bottom axis.
If you want to link both axes you just need to add this lines at the end of your code to refer again to the left axis:
yyaxis(g(1),'left')
yyaxis(g(2),'left')
linkaxes(g);
Alternatively, you could grab the handles to the numeric rulers, and use linkprop (without any call to linkaxes):
Y = get(g,'YAxis');
Y = [Y{:}];
linkprop(Y(1,:),'Limits')
linkprop(Y(2,:),'Limits')
You should add this after all axis are created, so all the handles will be assigned already.

Related

Two y-axis in Matlab: Setting different ranges and color

I am a noob when it comes to Matlab and I would appreciate any help! I need to create a figure with two y axis, and in order to satisfy my tutors I have to use specific ranges for them, and also to make it "more appealing" use colours that make some sense.
So I have two questions:
First, how can I set different ranges for the two y axis? I know I can use ylim([]} easily for 1 y axis but that doesn't seem to work.
Secondly, how can I easily change the color and format of one plot?(preferably they are the same as the color of the y axis they are assigned to, but Matlab automatically chooses them weirdly) Sadly sth like this won't work:
plot(x,y,'r','-','LineWidth',2.0);
It would be perfect if the first and second plot have the same format so '-' and the third and fourth another e.g. '--' but the plots Colors stay the same as their respective axis.
This is my current figure:
The following is my code
clc
A=dlmread('bipsim2_220.txt');
B=dlmread('bipsim2_680.txt');
x=A(:,1);
y=A(:,3);
plot(x,y,'LineWidth',2.0);
yyaxis left
hold on
x2=A(:,1);
y2=A(:,2);
plot(x2,y2,'LineWidth',2.0);
yyaxis right
hold on
x3=B(:,1);
y3=B(:,3);
plot(x3,y3,'LineWidth',2.0);
yyaxis left
hold on
x4=B(:,1);
y4=B(:,2);
plot(x4,y4,'LineWidth',2.0);
yyaxis right
yyaxis left
ylabel('Verstärkung (dB)')
yyaxis right
ylabel('Phase (deg)')
ylabel('Freq (Hz)')
set(gca,'Xscale','log')
set(gca,'fontsize',18)
hold off
grid minor
legend('R48/220 Ω: Phase [deg]','R48/220 Ω: Gain [dB]','R51/680 Ω: Phase [deg]','R51/680 Ω: Gain [dB]')
Thanks in advance for any help!
You can specify colors using RGB tuple with the color keyword agrument
You can specify linewidth using the linewidth keyword argument
You can specify styles as a positional argument after the data.
You can easily get X with logscale using semilogx
twinx will create a secondary Y-axis on with the labels on the right sharing the same X-axis.
import numpy as np
import matplotlib.pyplot as plt
freq = np.logspace(0, 5) # your frequency grid
# I made up a transfer function
H = lambda s: (s**2 - 1e2*s + 1e2) / (s - 1e3)**2
g = H(2j * np.pi * freq); # evaluate the transfer function at the frequency grid
# plot
plt.semilogx(freq, 20 * np.log10(abs(g)), '--k', linewidth=2)
plt.ylabel('Gain [dB]')
plt.xlabel('Frequency [Hz]');
plt.grid()
plt.twinx()
plt.semilogx(freq, 180 * np.angle(g) / np.pi, '-', linewidth=2, color=[0.8, 0.5, 0.3])
plt.ylabel('Phase [degrees]')
you can also specify predefined colors e.g k for black.
A few things to note:
You only need to call hold on once on the figure. Everything plotted after the first hold on will keep in the plot until you clear it with clf.
You can specify color and line style for each of your plots individually in its respective call to plot(...)
You need to set yyaxis left or yyaxis right before the thing you want to appear on that axis. This Matlab "from now on, we're now going to use the left/right axis"
On the same note, once you've set the approriate axis, you can manipulate its color and range.
In your code (untested because I don't have your input text files):
A=dlmread('bipsim2_220.txt');
B=dlmread('bipsim2_680.txt');
% resorted to have data and plotting separate (no need to do this, just easier to read the plotting part)
x1=A(:,1);
y1=A(:,3);
x2=A(:,1);
y2=A(:,2);
x3=B(:,1);
y3=B(:,3);
x4=B(:,1);
y4=B(:,2);
% set colors as a variables to change them easier
colorLeft = 'r'; % red
colorRight = 'k'; % black
% let's just open a clean figure
clf;
% set hold to on
hold on;
%% do stuff for the left y axis (gain)
yyaxis left;
% plot data with respective color and line style
plot(x1,y1,'LineWidth',2.0, 'Color', colorLeft, 'LineStyle', '-');
plot(x3,y3,'LineWidth',2.0, 'Color', colorLeft, 'LineStyle', '--');
% axis formating
ylabel('Verstärkung (dB)');
ylim([-200, 50]); % chose lower and upper limit for left y-axis
ax = gca; % all the formating of the axis is stored in an axis object which we can manipulate
ax.YColor = colorLeft; % set color of current (i.e. left) y-axis
%% now we move to do stuff for the right y axis (phase)
yyaxis right;
% plot data with respective color and line style
plot(x2,y2,'LineWidth',2.0, 'Color', colorRight, 'LineStyle', '-');
plot(x4,y4,'LineWidth',2.0, 'Color', colorRight, 'LineStyle', '--');
% axis formating
ylabel('Phase (deg)');
ylim([-180, 0]); % chose lower and upper limit for right y-axis
ax.YColor = colorRight; % set color of current (i.e. right) y-axis
%% finally, set all the format stuff not related to a particular y-axis
xlabel('Freq (Hz)')
ax.XScale = 'log';
ax.FontSize = 18;
grid minor
% hold off % no need to turn hold off, its only affecting the current figure anyway
%make sure that the order of legend entries fits the order in which you plot the curves
legend('R48/220 Ω: Gain [dB]','R51/680 Ω: Gain [dB]', 'R48/220 Ω: Phase [deg]','R51/680 Ω: Phase [deg]');

How to set ylim of only left axis object?

I use to yyaxis to create chart with two y-axes. Now I want to change ONLY the YLim of left axis to be zero.
I tried to use:
ax = gca;
ax.YAxis(1).YLim(1) = 0;
But I got an error message:
Assignment not supported because the result of method 'YLim' is a temporary value.
How to resolve this problem?
From the documentation:
yyaxis left activates the side of the current axes associated with the left y-axis. Subsequent graphics commands target the left side.
So, use
yyaxis left
ax = gca;
ax.YLim(1) = 0;

plotting arrows in MATLAB

I can draw two points in space and place arrows at them:
plot(1,1,'o','MarkerEdgeColor','k','MarkerFaceColor','k','MarkerSize',5,'LineWidth',1.5); hold on;
plot(2,1,'o','MarkerEdgeColor','k','MarkerFaceColor','k','MarkerSize',5,'LineWidth',1.5); hold on;
vec1=zeros(1,3); vec2=zeros(1,3); col1=zeros(1,3); col2=zeros(1,3);
vec1=[0.98996547 0.00000000 0.14130945];
vec2=[0.00000000 0.70710678 -0.70710678];
col1= [abs(vec1(1,1)) abs(vec1(1,2)) abs(vec1(1,3))];
col2= [abs(vec2(1,1)) abs(vec2(1,2)) abs(vec2(1,3))];
scalef=0.4;
quiver3(1,1,0,vec1(1,1)*scalef,vec1(1,2)*scalef,vec1(1,3)*scalef,'AutoScale','off', 'MaxHeadSize',5,'LineWidth',5,'Color',col1); hold on;
quiver3(2,1,0,vec2(1,1)*scalef,vec2(1,2)*scalef,vec2(1,3)*scalef,'AutoScale','off','MaxHeadSize',5,'LineWidth',5,'Color',col2); hold on;
view(20,20);
hold off;
The beginning of each arrow is the black point. How can I move the beginning of the arrow before the point so that the visual effect is better? Stated otherwise how can I place the points in the body of the arrow?

Two y-axes plot for multiple data set in Matlab

I am trying to create two y-axes plot in Matlab.
I have two groups of data, with each group having three plots of similar type. When I am trying to plot it, the scaling on right hand side y-axis get messed up. I would appreciate some help.
X = [50, 100, 200, 400];
YSKL_Temporal_WOFAE = [3.2000 2.3354 1.9428 1.7658];
YSKL_Spatial_WOFAE = [0.9225 0.9724 1.0986 1.1770];
YSKL_Spatial_WithFAE = [0.2635 0.1653 0.1513 0.1618];
YMSRE_Temporal_WOFAE = [0.3559 0.3027 0.2733 0.2636];
YMSRE_Spatial_WOFAE = [.3151 .2689 .2551 0.2524];
YMSRE_Spatial_WithFAE = [.0933 .0648 0.0663 0.0640];
figure(1);
[AX, p1, p2] = plotyy(X, YSKL_Temporal_WOFAE, X, YMSRE_Temporal_WOFAE);
set(AX,'XTick', X); % This fixes X-axis tick mark (same as data axis)
set(get(AX(1),'Ylabel'),'String','SKL Score')
set(get(AX(2),'Ylabel'),'String','Norm. Residuals')
xlabel('Time (\musec)')
title('SKL and Norm. Residual plotted on different y-axes')
set(p1,'LineStyle','--')
set(p2,'LineStyle',':')
axes(AX(1))
hold on
plot(X, YSKL_Spatial_WOFAE);
hold on
plot(X, YSKL_Spatial_WithFAE);
ylim([0 4])
hold off
axes(AX(2))
hold on
plot(X, YMSRE_Spatial_WOFAE);
hold on
plot(X, YMSRE_Spatial_WithFAE);
ylim([0.0 0.4])
hold off
Plot looks like this:
Please notice the scale on right y-axes
Regards,
Dushyant
The second (right hand side) y-axis tick labels are "frozen" after the call to plotyy. When adjusting the ylim on AX(2) this has no effect on the labels.
Therefore, the axes appearance has to be reset to auto.
Using the following code with the example from the question:
axes(AX(2))
hold on
plot(X, YMSRE_Spatial_WOFAE);
hold on
plot(X, YMSRE_Spatial_WithFAE);
ylim([0.0 0.4])
% include the following statement to allow
% the second y-axis to reset the ticks:
set(AX(2), 'YTickMode', 'auto', 'YTickLabelMode', 'auto')
hold off
Will yield this plot:

Matlab - Legend does not match my graph

I am having trouble matching my graph with my axis. The first two plots work and the second two do not. I am trying to plot Temperature versus Pressure for two Argo floats and then Salinity versus Pressure. Here is my code:
% First Plot
subplot(221);
plot(float1winter.T,float1winter.P,'b');
hold on;
plot(float1summer.T,float1summer.P,'r');
hold on;
tempAdiff = abs(float1summer.T-float1winter.T)
plot(tempAdiff,float1summer.P,'--k');
hold on;
set(gca,'ydir','reverse');
title('Argo Float #1901440 Temp Profiles');
legend(['float1winter','float1summer','tempAdiff'],{'11-29-2013','07-01-2013','Temperature Difference'},'location','southwest');
xlabel('Temperature (°C)');
ylabel('Pressure');
shg;
% Second Plot
subplot(222);
plot(float2winter.S,float2winter.P,'m');
hold on;
plot(float2summer.S,float2summer.P,'c');
hold on;
set(gca,'ydir','reverse');
title('Argo Float #1901440 Salinity Profiles');
legend(['float2winter','float2summer'],{'11-29-2013','06-02-2013'},'location','southwest');
xlabel('Salinity (psu)');
ylabel('Presure');
shg;
% Third Plot
subplot(223);
% Matrix demensions did not agree bewteen winter and summer profiles. The summer profile was 71 x 2 and the winter was 70 x 2. I tried "reshape"
% and that didn't work. So I changed the vector of float3summer.T to
% float3bsummer.T with an array of 70 x 2
float3bsummer.T = float3summer.T(1:70,1:2);
float3bsummer.P = float3summer.P(1:70,1:2);
plot(float3winter.T,float3winter.P,'Linewidth',1,'color','blue');
hold on;
plot(float3bsummer.T,float3bsummer.P,'Linewidth',1,'color','red');
hold on;
tempdiff = abs(float3bsummer.T-float3winter.T)
plot(tempdiff,float3bsummer.P,'--k');
hold on;
set(gca,'ydir','reverse'); % this line reverses the y-axis so that depth increases downward
title('Argo Float #1901415 Tempearture Profiles');
hold on;
summerfloat = plot(float3bsummer.T,float3bsummer.P,'r');
legend(['float3winter.T','summerfloat','tempdiff'],{'12-03-2013','07-03-2013','Temp Diff'},'location','southeast');
xlabel('Temperature (°C)');
ylabel('Pressure');
axis ([-1,4,0,2000]);
shg;
% Fourth Plot
subplot(224);
plot(float3winter.S,float3winter.P,'g');
% Changed matrix dimensions for Salinity of Summer
float3bsummer.S = float3summer.S(1:70,1:2);
float3bsummer.P = float3summer.P(1:70,1:2);
plot(float3bsummer.S,float3bsummer.P,'.b');
hold on;
set(gca,'ydir','reverse');
title('Argo Float #1901415 Salinity Profiles');
h4 = plot(float3winter.S,float3winter.P,'g');
hold on;
h5 = plot(float3bsummer.S,float3bsummer.P,'.b');
hold on;
legend(['float3winter','float3bsummer.T'],{'12-03-2013','07-03-2013'},'location','southwest');
xlabel('Salinity (psu)');
ylabel('Pressure');
axis ([33.8,34.8,0,2000]);
shg;
% Save File to Desktop
set(gcf,'color','w');
saveas(gcf,'~/Desktop/hw1_figure1.pdf','pdf');![enter image description here][1]
I guess that you're trying to associate the set of strings for your legend, {'11-29-2013','07-01-2013','Temperature Difference'}, with the plots made from the variables ['float1winter','float1summer','tempAdiff'].
However, this isn't how legend works. MATLAB has no way of associating the plot produced by plot(float1winter.T,float1winter.P,'b'); to the string float1winter. If you want to specify which plots go with which legend entries, you need to pass the object handles of the plots to legend, which is easiest done by returning the handles when you plot originally:
h(1) = plot(float1winter.T,float1winter.P,'b');
hold on;
h(2) = plot(float1summer.T,float1summer.P,'r');
h(3) = plot(tempAdiff,float1summer.P,'--k');
legend(h,{'11-29-2013','07-01-2013','Temperature Difference'});
Side note: you only need to call hold on once per axis - so once for each subplot but not after every plot call.
Alternatively, you can not give handles at all; legend will assign the text to the plots in the order that they were plotted:
legend({'11-29-2013','07-01-2013','Temperature Difference'})
Understanding graphics handles allows you a lot more control over plots, especially if you might want to make small adjustments to them. For example, if I decide that I want the first plot to be green rather than blue, then I can just do:
set(h(1),'Color','g');
This will change the plot color and the legend changes to match automagically. To see a list of all the properties of an object, use get with only the handle. You can set more than one property at a time. For example:
get(h(1))
set(h(1),'DisplayName','Winter','LineWidth',3,'Marker','x')