Semilogy with two functions - how to make it work?

Question

Chris 2013-9-16

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评论： Connor Williams 2019-9-25

I have two functions, y1 and y2, both of which are quadratic functions. I'm trying to graph them on the same plot, with the y-axis being on a logarithmic scale instead of a linear scale. I know how to get just one of the functions to have a log scale on the y axis, but whenever I have two functions involved, the y-axis reverts to a linear scale. I have the code I've been using below; how might I format the semilogy so that the plot will have both functions graphed while still having the y-axis as a logarithmic scale? Any help would be appreciated.

Code:

x1=0:0.1:50;
x2=0:0.1:50;
y1=15*(x1.^2);
y2=80*(x2.^2);
semilogy(y1,y2)
plot(x1,y1,'-','LineWidth',3,'Color','k')
hold on
plot(x2,y2,'-','LineWidth',3,'Color','k')

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Answer 1

the cyclist 2013-9-16

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https://ww2.mathworks.cn/matlabcentral/answers/87291-semilogy-with-two-functions-how-to-make-it-work#answer_96831

在 MATLAB Online 中打开

x1=0:0.1:50;
x2=0:0.1:50;
y1=15*(x1.^2);
y2=80*(x2.^2);
figure
hold on
semilogy(x1,y1,'-','LineWidth',3,'Color','k')
semilogy(x2,y2,'-','LineWidth',3,'Color','k')

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Connor Williams 2019-9-25

This is incorrect. If you initiate the figure with figure and hold on commands before the semilogy command, the figure remains with linear axes.

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Answer 2

Chris 2013-9-16

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此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/87291-semilogy-with-two-functions-how-to-make-it-work#answer_96833

I think that'll work for now, thank you.

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the cyclist 2013-9-16

Just for your future reference, your remark would have been better placed as a "comment" on my answer (rather than as a new "answer"). You might also consider accepting my answer if it was helpful to you, which may be useful for future users looking for something similar.

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