Beginner - stuck on Matlab

It's a question on MatLab Integration program, but have a look at this code first. It's a part of the Integration on Rectangle Method program:

 [LINES 1-3] 
 x = 1 : 2 : 5; % x=lower limit: strip width: upper limit
 % These are not supposed to be constants, but for this question's simplicity, let's keep it that way.

 [LINE 4]
 y_x = input ( 'Enter your function of x = ' ) 
 % allowing the user to modify the function as required

 [LINE 5]
 S = 2 .* ( sum (abs (y_x)) )

Now, that works fine with the subsequent lines to calculate the approximation of the integration; but, I want what was input by the user for y_x to be also used for the plot TITLE, DISP, and others. The issue is y_x turns to an array instantly. If I turn the input into string [Ex: y_x = input ( ' Enter you function of x = ' , 's') ], it works with the DISP and TITLE, but it doesn't process the x array, so I don't get the integration approximation. Example, say x.^2 was input. Hence, y_x = x.^2

 [LINE 6 - 7]
 plot( x , y_x)
 title(['Numeric Integration for' , num2str(y_x) , 'with 2 slices')

Instead of title being 'Numeric Integration for x.^2 with 2 slices', what shows is 'Numeric Integration for 1 9 25 with 2 slices.' [1 9 25] is the squares for x=1 : 2 : 5. That's because the input has turned to an array and info is lost. Anyone knows how to get around this problem?

Another problem is I also want the equation to be used on the FOR function:

for x = 1 : 2 : 5
    y_x = ??? (something to go through the array and produce an array of y_x)
    plot( [x x], [0 y_x])
end

That FOR function is to make vertical lines from the x-axis to the coordinate (x, y_x).

Thanks a lot!

Answer 1

[Walter Roberson]

y_xs = input('Enter your function of x =', 's');
y_x = str2func( ['@(x) ', y_xs] );

Now, to calculate,

   y_x(x)

and include y_xs in the title

[Dominic]

You're awesome! It works now. Cheers