How do you plot a circle with a str2func()?

I was wanting to plot a circle using the str2func(). I'm able to plot the x section but the y section will not work. Thanks!

edit: I"m asking this for a friend, I'm trying to help him with a script that he's trying to write, but I"m not sure how to implement the str2func() to pick up the y values as well as the x values if a user inputs the x and y values.

Answer 1

[Matt J]

No idea why you think str2func should be part of the task. Why not simply,

fimplicit(@(x,y) x.^2+y.^2-100,11*[-1,+1,-1,+1]); axis equal

[Matt J]

Perhaps you were aiming for something like this?

fun=str2func( '@(x,y) x.^2+y.^2-100' );

fimplicit(fun,11*[-1,+1,-1,+1]); axis equal

[KG]

I'm asking for a friend and he's trying to have someone input an equation into the command section using a function and then do a vertical line test to determine if the inputted equation is a function. He's wanting the user to input a string and then plot that string (by converting it using the str2func())and have his script determine if it passes the vertical line test. I think this may be what he is aiming for.

[KG]

I know it's confusing.

[Walter Roberson]

S = input('Enter a function in x and y: ', 's');
fun = str2func( "@(x,y) " + S);