inline.inline at 47

Hello people,

Can someone explain what's kind of error is this:

inline.inline at 47 Input must be a string.

P.S. I use diff function in my code.

Thanks.

Answer 1

[Walter Roberson]

syms x
fun = sym( get(handles.edit4,'String') );
f = matlabFunction(fun, x);
dfun = diff( fun, x );
df = matlabFunction(dfun, x);

Answer 2

[Wayne King]

The kind of error you are reporting comes from trying to input a non-string input in inline()

For example:

t = 10;
g = inline(t^2);

Are you trying to do symbolic differentiation?

[Aldin]

Here is one part of my code:

f = inline(get(handles.edit4,'String'),'x');

y = char(f);

df = inline(diff(y),'x');

[Aldin]

It seems to be OK!?

[Walter Roberson]

Your "y" is a string. A string is an array of characters. diff(y) applied to an array of anything other than symbolic expressions gives [y(2)-y(1), y(3)-y(2), y(4)-y(3)] and so on.

*Only* symbolic expressions can be differentiated.

[Wayne King]

Hi, No, because diff(y) here is going to return a double-precision vector, which results in the error I showed you above.