How to draw with semiology in MATLAB?
2 views (last 30 days)
Show older comments
Haitham AL Satai
on 21 Sep 2022
Commented: Haitham AL Satai
on 21 Sep 2022
I have below the following information:
Q = [16,32,64,128,256,512,1024];
y = [9 9 9 9 5 0 0]*0.25;
y1 = [45 37 25 21 5 0 0]*0.25;
After multiplication with 0.25 they became as below
y
![](https://www.mathworks.com/matlabcentral/answers/uploaded_files/1131225/image.png)
y1
![](https://www.mathworks.com/matlabcentral/answers/uploaded_files/1131230/image.png)
and the above Q is the same
![](https://www.mathworks.com/matlabcentral/answers/uploaded_files/1131235/image.png)
when I use the semiology plot function as below
semilogy(Q,y,Q,y1)
xlabel('Q oder');
ylabel('Coverage area m^2');
grid on;
I saw the x and y axis are different than what I have in Q and Y as shown below. Does this make sense?
Do I apply it in the wrong way (I mean xlim and ylim not as the values in vectors for example x-axis (16 , 32, ...1024))? If yes, May you assist me?
![](https://www.mathworks.com/matlabcentral/answers/uploaded_files/1131240/image.png)
4 Comments
Accepted Answer
Chunru
on 21 Sep 2022
Edited: Chunru
on 21 Sep 2022
Q = [16,32,64,128,256,512,1024];
y = [9 9 9 9 5 0 0]*0.25;
y1 = [45 37 25 21 5 0 0]*0.25;
% in logscale, log(0) = -inf and it cannot be plotted
semilogy(Q,y,Q,y1)
xlabel('Q oder');
ylabel('Coverage area m^2');
grid on;
xlim(Q([1 end]))
% Why not plot in linear scale when data range is not big?
figure
plot(Q,y,Q,y1)
xlabel('Q oder');
ylabel('Coverage area m^2');
grid on;
% or you should change your data
Q = [16,32,64,128,256];
y = [9 9 9 9 5 ]*0.25;
y1 = [45 37 25 21 5 ]*0.25;
figure
semilogy(Q,y,Q,y1)
xlabel('Q oder');
ylabel('Coverage area m^2');
grid on;
More Answers (1)
Dyuman Joshi
on 21 Sep 2022
The graph is correct. The y axis values are shown in log values as you wanted them to be.
And, for the last two values of Q, the corresponding values are 0 in y and y1. So they are not included for the log values.
If you want to identify the points in x axis, you can try changing the xticks, but it might result in a distorted grid. (You can do the same for yticks as well.)
Q = [16,32,64,128,256,512,1024];
y = [9 9 9 9 5 0 0]*0.25;
y1 = [45 37 25 21 5 0 0]*0.25;
semilogy(Q,y,Q,y1)
xlabel('Q oder');
ylabel('Coverage area m^2');
grid on;
%yticks(union(y,y1))
xticks(Q)
See Also
Community Treasure Hunt
Find the treasures in MATLAB Central and discover how the community can help you!
Start Hunting!