How to draw with semiology in MATLAB?

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

y1

and the above Q is the same

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?

[Stephen23]

"I saw the x and y axis are different than what I have in Q and Y as shown below."

No, in fact the plotted values are exactly the same as Q and Y.

Of course zero is not plotted (just as the documentation states) because your graph is not infinitely large.

"Does this make sense?"

Yes: the vertical values go from just above 10 to just above 1, which exactly matches your data values. So far everything makes complete sense and is exactly as expected.

"Do I apply it in the wrong way?"

You did not explain what you expect nor what you think the problem is: we cannot guess what you want.

[Haitham AL Satai]

@Stephen23 Thank you dear for your comment. I meant in the last question (I mean xlim and ylim not as the values in vectors for example x-axis (16 , 32, ...1024))

[Stephen23]

"I mean xlim and ylim not as the values in vectors for example x-axis (16 , 32, ...1024))"

Because the 0-values are not plotted the corresponding x-values are ignored, so your x data range is from 16 to 256.

[Haitham AL Satai]

@Stephen23 Thanks a lot for your clarification dear.

Answer 1

[Chunru]

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;

[Haitham AL Satai]

@Chunru Thank you dear sir. I just wanted to take the both kind of results semiology and line plot and compare between them.

Answer 2

[Dyuman Joshi]

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)

[Haitham AL Satai]

@Dyuman Joshi Thank you very much dear sir.