label each curve on semilog graph

Hi

I have multiple columns/arrays that I need to plot using semilogx. I tried plotting using the following :

semilogx(array_1,array_2,'.',LineStyle='-',DisplayName='no_1')

hold on

....

I am getting plots but without labels for individual curves. I was wondering if there was a better way of labeling the curves at their first point/beginning. really appreciate some help here.

Answer 1

[Star Strider]

I am not certain what you want, however creating a legend entry for each line does not appear to be the desired result.

It is relatively straightforward to use text objects to label plots —

x = logspace(-3,1,500).';
y = [exp(-0.1*x).*sin(2*pi*x)  exp(-0.2*x).*cos(2*pi*x)];

figure
semilogx(x, y)
grid
axis('padded')
text(x(1), y(1,1),  "\leftarrow Sine Curve With Exponential Attenuation", 'Horiz','left', 'Vert','middle', 'Rotation',-30)
text(x(1), y(1,2),  '\leftarrow Cosine Curve With Exponential Attenuation', 'Horiz','left', 'Vert','middle', 'Rotation',-30)

Make appropriate changes to get the result you want.

.

[Sonali]

This is what I want, But I have 22 plots on same graph. the labels are not showing. Its on semilogx. yet its not showing the individual labels. A legend will not work for me as the number of plots are large and the colors of plots are repeating.

[Dyuman Joshi]

If you have 22 plots on the same graph, then the figure will likely get cluttered with 22 text labels.

[Star Strider]

It might help to have the data. I cannot figure out how to simulate that plot.

You can have the colours not repeat by choosing a different colormap, and then specifying the colours ffor each line object.

The other problem however are the labels. You can still use text with them, however the number of them is going to be a problem.

x = logspace(-1, 3, 22).';
y = 1E3*randn(1,22) .* x;

figure
semilogx(x, y)
Ax = gca;
Ax.XAxis.TickLabels = [];
cmpds = {'H^+','H_3O^+','CO^+\ N_2^{++}'}

cmpds = 1×3 cell array
    {'H^+'}    {'H_3O^+'}    {'CO^+\ N_2^{++}'}

NC  = numel(cmpds);
xv = rand(1,NC)+logspace(-1,2,NC);
yv = ones(1,NC)*(-0.05*diff(ylim)+min(ylim));
for k = 1:NC
    text(xv(k), yv(k), sprintf('$\\uparrow$\n$%s$',cmpds{k}), 'Interpreter','latex')
end

I cannot incorporate a newline in the third ‘cmpd’ so that it will print on two lines. The best I can do is a space.

Annotation objects might be able to do the longer arrows at specific angles, however they will not operate outside of the axis llimits (unlike text), so it might be possible to use them with an ‘axes in axes’ plot (see Position Multiple Axes in Figure for an illustration) and use them in the larger axis referring to the smaller axes, however this would require considerable effort, as well as all the data.

.

Answer 2

[Sulaymon Eshkabilov]

Here are a couple of the possible ways to get this exercise done:

t = logspace(0, 2, 1e3);
Y1 = exp(sin(t));
Y2 = exp(cos(t));
figure % Way 1
semilogx(t, Y1, 'r-o', 'DisplayName', 'Y_1(t) = e^{sin(t)}')
hold on
semilogx(t, Y2, 'b--*',  'DisplayName', 'Y_2(t) = e^{cos(t)}')
legend('Show')
xlabel('t')
ylabel('Y_1(t), Y_2(t)')
grid on

figure  % Way 2
semilogx(t, Y1, 'r-o')
hold on
semilogx(t, Y2, 'b--*')
legend('Y_1(t) = e^{sin(t)}', 'Y_2(t) = e^{cos(t)}')
xlabel('t')
ylabel('Y_1(t), Y_2(t)')
grid on