How to plot a function is equal to a constant?

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John
John 2014-9-11
回答： John 2014-9-11
I am new to MATLAB and am trying to graph ln(x^2)=0.7 to find the roots graphically. I have tried to following.
x=-5:5;
y=log(x.^2)-0.7;
plot (x,y)
this gets me close but the graph isn't coming out right. I also tried to y=log(x.^2)=0.7 or y=log(x.^2)-0.7=0 but this doesn't work either. Any help is appreciated!

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采纳的回答

Roger Stafford
Roger Stafford 2014-9-11
The range for x = -5:5 includes the value x = 0 for which log(0) is minus infinity. I would suggest
x = linspace(1,2,1000);
y = log(x.^2)-.7;
plot(x,y)
Look for where it crosses y = 0.
Of course there is a much easier method:
x = sqrt(exp(0.7));

更多回答（1 个）

John
John 2014-9-11
I got it to work by using ezplot('(log(x.^2)-0.7)'). Thank you though!

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