Taking expression input and plotting it within an interval using app designer

I need to take a single variable expression as input from the user and give the plot for the same. I am able to take the expression input and make it a function using inline, but when I go for plotting it within an interval it shows the following error:

Error using inlineeval (line 14)

Error in inline expression ==> x^2 - 11*x + 30

Incorrect dimensions for raising a matrix to a power. Check that the matrix is square and the power is a scalar. To perform elementwise matrix powers, use '.^'.

Error in inline/subsref (line 23)

INLINE_OUT_ = inlineeval(INLINE_INPUTS_, INLINE_OBJ_.inputExpr, INLINE_OBJ_.expr);

My code for input was:

s = app.EnterHereEditField.Value;

f = inline(s);

and for plotting:

x = -10:.1:10;

y = f(x);

plot(app.UIAxes,x,y);

I am new to matlab app designer, if there's some syntax error please tell. Thanks!

Answer 1

[Shanmukha Voggu]

Hi Aditya,

The error(Incorrect dimensions for raising a matrix to a power. Check that the matrix is square and the power is a scalar. To perform elementwise matrix powers, use '.^'.) is regarding the expression(x^2 - 11*x + 30)

To understand the difference between x.^2 and x^2, let's create a square matrix x

x=[1,2;3,4]
ElementWiseSquare=x.^2 % Every element in the matrix is raised to power "2"
MatrixMultiplication=x^2 % For matrix multiplication, the number of columns in the first matrix must be equal to the number of rows in the second matrix

let's create a row matrix x

x=[1,2]
ElementWiseSquare=x.^2 % Every element in the matrix is raised to power "2"
MatrixMultiplication=x^2 % This statement gives an error because columns in [1,2](first matrix) not equal to rows in [1,2](second matrix)

There can be two fixes for the issue:

1) replace the x^2 in the expression(x^2 - 11*x + 30) with x.^2

2) or make sure x is a square matrix.

refer this for more information.

[Aditya Prakash]

Got it, thanks!