Discover MakerZone

MATLAB and Simulink resources for Arduino, LEGO, and Raspberry Pi

Learn more

Discover what MATLAB® can do for your career.

Opportunities for recent engineering grads.

Apply Today

New to MATLAB?

About isinteger command(confusion)

Asked by C Zeng

C Zeng

on 14 Mar 2013
Latest activity Edited by per isakson

per isakson

on 16 Jan 2015 at 14:56
Accepted Answer by per isakson

per isakson

Hi, by the command of isinteger I can check if it is an integer, however, when defined at first, Matlab assume it is double precision right? So even a=3, isinteger(a) returns 0.

How to solve this problem?

0 Comments

C Zeng

C Zeng

Tags

Products

No products are associated with this question.

3 Answers

Answer by per isakson

per isakson

on 14 Mar 2013
Edited by per isakson

per isakson

on 16 Jan 2015 at 14:56
Accepted answer

Matlab represents integers in differnt ways:

  • int8, int16, etc. see Christians answer
  • with a special use of double, which is called flint. See Floating Points

I use this function to test for flint

    function    isf = isflint( m )
    %   floating double only
        try
            bitand( abs( m ), 1 );
            isf = true;
        catch me
            isf = false;
        end
    end

I picked up the idea from a contribution by the "Pedestrian" in the FEX.

(I stripped off comments and error handling.)

5 Comments

C Zeng

C Zeng

on 15 Mar 2013

Thanks, Isakson, will take a look.

Jan Simon

Jan Simon

on 16 Mar 2013

The problem is to decide, if 1e17 is an integer or not: Because a double can store 16 digits only, this number does not contain any information about the fractional part for reasons of the precision. bitand() detect this and throw an error, while 1e17==round(1e17) replies true, because cropping the fractional part does not influence value.

C Zeng

C Zeng

on 17 Mar 2013

Thanks, I understand it. It is good to know.

per isakson

per isakson

Answer by Jan Simon

Jan Simon

on 16 Mar 2013

Joining the rounding with the checks for overflows:

function isf = isflint(m)
isf = (abs(m) <= bitmax && m == floor(m)); 

1 Comment

per isakson

per isakson

on 18 Mar 2013

I'll replace my cryptic isflint.

Jan Simon

Jan Simon

Answer by ChristianW

ChristianW

on 14 Mar 2013
doc isinteger
isinteger(int8(3))

5 Comments

C Zeng

C Zeng

on 16 Mar 2013

yes, I used x==round(x) or floor(x). what do you mean by "isint = @(x)"?

Jan Simon

Jan Simon

on 16 Mar 2013

@C Zeng: @(x) x==round(x) is an anonymous function. You find an exhaustive description ion the documentation.

C Zeng

C Zeng

on 17 Mar 2013

OK

ChristianW

ChristianW

Contact us