Simple MatLab Issue Regarding fplot and function files

Question

The explicit problem is as follows: Write a function and use the fplot command to plot f(x)=x^3-x+8 versus x, for values of x from 0 to 100.

The easy way, throw the following code into matlab and call it a day:

Testing = @(x) x^3 - x + 8
fplot(Testing, [0 100])

and done!

but I want to take a slightly more 'difficult' approach. Basically I made a seperate .m file that has the following:

function [y] = blah(x)
y = (x^3) - x + 8;
end

and a script with the following

fplot('blah', [0 100])

but it doesn't work. whyyyy ( i keep getting a positive-sloped line)

Thanks!

I tried it on my pc and both are giving the same results!, so what is the problem ? — Hazem
– Hazem, Commented Dec 6, 2017 at 9:40
You need an @ with your call to that function. See the duplicate target and gnovice's comment on the accepted answer — Sardar Usama
– Sardar Usama, Commented Dec 6, 2017 at 10:22
Possible duplicate of MATLAB odd 'Too many input arguments' error — Sardar Usama
– Sardar Usama, Commented Dec 6, 2017 at 10:23

Laure · Accepted Answer · 2017-12-06 10:14:08Z

0

In my version of Matlab (2016b), it works when blah is not a string:

blah = @(x) (x.^3) - x + 8;

plot(0:100, blah(0:100),'r.-')
hold all
fplot(blah,[0 100],'kx-')

edited Dec 6, 2017 at 10:14

answered Dec 6, 2017 at 10:08

Laure

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3 Comments

Sardar Usama Over a year ago

This is not what the OP is asking. The OP is asking why it does not work with function [y] = blah(x)

Laure Over a year ago

@SardarUsama, issue is the same whether blah is in an independent file or an inline function. fplot plots x = 1:100 and y = 1:100 in both cases. Using the function handle solves the issue.

Sardar Usama Over a year ago

The OP already knows that it works with blah = @(x) (x.^3) - x + 8; and clearly is not asking what you have answered

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