how to plot a function handle on matlab 7 ?

2018 4 20
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更新时间：2018 4 21
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1 个投票

my code is i'm asking the user to input a funtion and i transform it to a handle one (note that i'm using the matlab 7.0 R14) :
funstr = input('• Please enter your function here : ', 's');
f = eval( ['@(x) ' funstr ] );
how can i possibly do the plot of this between the two points a and b? i keep getting errors
??? Index exceeds matrix dimensions
or
??? Error using ==> plot Conversion to double from function_handle is not possible.
i tried it with plot and fplot and none of them is working !
thanks for helping in advance.

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Star Strider
Star Strider 2018-4-20

3 个投票

You need to evaluate the function in the plot call.

Example —

fun = @(x) x.^3 - 8*x.^2 + 10;
x = linspace(-5, 5);

figure
plot(x, fun(x))
grid

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HeadingUpHigh
HeadingUpHigh 2018-4-20

first of all thanks for your quick answer, i tried it but it keeps giving me this error : ??? Error using ==> plot

 Conversion to double from function_handle is not possible.
 Error in ==> SimpsonComposee at 136
      plot(x, f)
Star Strider
Star Strider 2018-4-20

My pleasure.

I have no idea what ‘f’ is. If it is a function of one variable, try this:

plot(x, f(x))

It is now no longer a function handle, but a function evaluation.

HeadingUpHigh
HeadingUpHigh 2018-4-20

thanks man it worked, also i have another question if possible :

      ax = gca;
      ax.XAxisLocation = 'origin';
      ax.YAxisLocation = 'origin';

this is to Set the y-axis so it passes through the origin of the x-axis (x = 0). but it's not working for me in matlab 7 what's wrong ?

Star Strider
Star Strider 2018-4-20

As always, my pleasure.

I believe it was introduced in R2016b.

There are other options that will work in previous versions, the most popular being axescenter (link). A full File Exchange search for similar functions is here (link).

HeadingUpHigh
HeadingUpHigh 2018-4-21
thanks mate, you've been very helpful.
Star Strider
Star Strider 2018-4-21
As always, my pleasure.
The File Exchange has several functions that add necessary capabilities missing in earlier MATLAB versions. (Many of these have been incorporated in MATLAB and the Toolboxes since.)

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