How to use input string as a function in Appdesign?

I am beginner in appdesigning. However, I am trying here to make an interface where user will write down the equation of a function and the value of the variable. After clicking the button,he will get the value of f(x) for the given value. Maybe I have some errors in the codes for which,after giving datas and clicking then,there seems something wrong. Someone please help me to debug this I need that emergency.

Answer 1

[Simon Chan]

In case you would like to use function str2func, the string in the editfield for entering the equation should looks like the following:

@(x)x^2

instead of

x^2

and use the following inside the callback

f = str2func(s)

instead of

f = @(x)(str2func(s))

[Abrar]

Awwwww it worked. Thanks a loooot <3

Answer 2

[Steven Lord]

If the user enters an expression in the edit field, you can convert it into an anonymous function using a couple of functions.

s = 'x^2+y';

Make it so it can be called with a vector of values using the vectorize function.

vecFunction = vectorize(s)

vecFunction = 'x.^2+y'

Get the list of variables using symvar.

vars = symvar(s)

vars = 2×1 cell array
    {'x'}
    {'y'}

Assemble the string representation of the anonymous function, joining the list of variables and the function that was entered into the edit box.

str = "@(" + join(vars, ", ") + ") " + vecFunction

str = "@(x, y) x.^2+y"

Make the anonymous function with str2func.

f = str2func(str)

f = function_handle with value:
    @(x,y)x.^2+y

To check let's call the function handle.

z = f(1:10, 100)

z = 1×10

101 104 109 116 125 136 149 164 181 200