how can i change Y-axis into log and dont get Warning: Negative data ignored

조회 수: 7 (최근 30일)
zhu ting
zhu ting 2015년 10월 1일
편집: Walter Roberson 2015년 10월 14일
I am writing a Programm that turned both Axis into log10, here is my Programm:
x=real(lambda)/W0;
y=imag(lambda)/W0;
figure
plot(x,y,'*')
set(gca,'xscale','log')
set(gca,'yscale','log')
grid on
Lambda and W0 are two Input Data.
This Programm run very well when i just delete 'set(gca,'yscale','log')', but with this sentence then a Warning Negative data ignored will be pupped out. Is there any way that will let my y-axis being turned into 'log' and at the same time with negative data?
PS: i also tried LOGLOGPN but my plot is a lots of dots not a line so its also not working.
Mit freundlichen Grüßen
Ting Zhu
  댓글 수: 1
zhu ting
zhu ting 2015년 10월 1일
편집: Walter Roberson 2015년 10월 14일
and here is what my data for example:
lambda=[-1;-2;-3+2j;-3-2j;-4+3j;-4-3j];
W0=1;

댓글을 달려면 로그인하십시오.

답변 (1개)

Kirby Fears
Kirby Fears 2015년 10월 1일
Hi Zhu,
The log function is undefined for negative values. Have a look at the wiki page .
Matlab can't apply log to the negative values, so it just ignores them.
Hope this helps.
  댓글 수: 2
zhu ting
zhu ting 2015년 10월 9일
but all my X-data are negative values and ist working without any Warning. Do u know why?
Here is my Input for example:
lambda=[-1;-2;-3+2j;-3-2j;-4+3j;-4-3j];
W0=1
Thanks
Kirby Fears
Kirby Fears 2015년 10월 13일
Log is not applied to the X values. Look at the X axis before and after the statement
set(gca,'xscale','log')
You will see that the X axis still has the exact same values as before. The values are only repositioned along the axis.
This allows you to plot log(y) against the original x values that generated y, but spaced in such a way that the plot is more readable.
Hope this helps.

댓글을 달려면 로그인하십시오.

태그

제품

Community Treasure Hunt

Find the treasures in MATLAB Central and discover how the community can help you!

Start Hunting!

Translated by