# m file failure?

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• Apr 26th 2010, 02:54 AM
CaptainBlack
Quote:

Originally Posted by ramdrop
I got a very nice plot, thanks, so I guess I do the same for the next part of the file?

As it happens you don't need to, at the command prompt now type:

Code:

```>>plot(x,(f(x+0.1)-f(x))/0.1,'r') >>plot(x,(f(x+0.01)-f(x))/0.01,'g') >>plot(x,(f(x+0.001)-f(x))/0.001,'b') >>plot(x,(f(x+0.0001)-f(x))/0.0001,'m')```
If you want them on the same plot you will need

Code:

`>>hold on`
before hand, (and sort out axes)

CB
• Apr 26th 2010, 03:10 AM
ramdrop
But what about the derivative? Im trying to differentiate the function, maybe its not being shown as well because the original is \$\displaystyle e^x\$

If it was for say, \$\displaystyle x^2\$:

Quote:

function [y]=f(x)
y=exp(x);

then...

Quote:

>>x=[-10:0.5:10]
>>y=f(x)
>>plot(x,y);
then, i want to plot the derivative, and approximate it... using the values of x = 0.01, 0.001.. .etc, so the fd(x) is needed.
• Apr 26th 2010, 03:56 AM
CaptainBlack
Quote:

Originally Posted by ramdrop
But what about the derivative? Im trying to differentiate the function, maybe its not being shown as well because the original is \$\displaystyle e^x\$

If it was for say, \$\displaystyle x^2\$:

then...

then, i want to plot the derivative, and approximate it... using the values of x = 0.01, 0.001.. .etc, so the fd(x) is needed.