How do you get a number string to display the sign (pos and/or neg) in front of it.

What i am having trouble finding is how to get a title of a graph to display the sign for both positive and negative input. What i have done so far is this.

    %Determine what the quadratic is.
    disp('What are the quadratics coefficients?');
    a = input('Coefficient A=');
    b = input('Coefficient B=');
    c = input('Variable C=');
    disp('Thank you, calculating now.');

    %display graph and customize it
    plot(x,y, '--b', 'LineWidth', 3)
    grid on
    xlabel ('x')
    ylabel ('f(x)')
    title (['f(x)=' num2str(+a) 'x^2' num2str(+b) 'x' num2str(+c)])

The title is the quadratic function but like this only shows the "-" but i need it to show the "+" if it is a positive number.

Any pointers?

Answer 1

[Guillaume]

Use a format specifier with your num2str:

 >>num2str(1.5235646, '%+2.2f')
 ans = 

   +1.52

I would actually use sprintf to build the whole string:

title(sprintf('f(x)= %+2.2fx^2%+2.2fx%+2.2f', a, b, c))

[Sky Adams`]

Great, thanks for the fast reply! And thanks for the pointers to the right direction. :)

Answer 2

[pfb]

Perhaps use sprintf? For instance, if a, b, c are integers

 ttl = sprintf('f(x) = %+d x^2 %+d x %+d',a,b,c);
 title(ttl);

Use %f if a,b,c, are floating point and so on. Refer to the help of sprintf.

[pfb]

sorry for the duplicate, didn't see Guillaume's reply.

[Sky Adams`]

No need to apologize. I found your answer a bit more aligned with what i know which in turn made Guillaume's easier to understand. Thank you :)