How to use if statement to test if it is a integer and real number?

    x = input('enter the number: ');
    if isreal(x)
    else
        delete x
        if isinteger(x)
            delete x
        end
    end

I try to do it, but it doesn't work.How to make it? It just a part of the whole script. It requires to delete the number if it isn't a integer or real number.

Answer 1

[Star Strider]

MATLAB has a special integer class. (See the documentation for isinteger for details.) The numeric output x of your input statement will always return a double in x, so the isinteger call will always fail.

If you want to test for a whole number, use the rem function.

Here is one way to implement your if block:

if isreal(x) && rem(x,1)==0

else
    x = [];
end
x

The first line tests if x is real, then if it is, goes on to see if dividing it by 1 leaves a remainder. (The ‘&&’ operator will only evaluate the second part of the statement if the first part is true.) If both conditions in the first line are true, it leaves x alone. If one or the other condition fails, that means x is not real or x is not a whole number, and sets x to the empty matrix, deleting it from the workspace.

[Shi Yuhao]

Sorry, it's my fault. I mean that if the number is not real number or integer, it should redo the function. The input number should meet the needs of real number and integer.

[Star Strider]

This seems to do what you want it to:

reorint = 0;                            % ‘Real-or-Integer’ flag
while reorint == 0                      % Continue looping until ‘good’ number entered
    x = input('Enter the number: ');
    if isreal(x) && rem(x,1)==0
        reorint = 1;                    % ‘Real-or-Integer’ number
    else
        fprintf(1,'\nThe number is either complex or not a whole number.\n')
        reorint = 0;                    % ‘Complex or non-integer’ number
    end
end

You might want to put in a counter and test it to limit the number of attempts. Otherwise it will loop endlessly until it gets a ‘good’ number for x.

[Hafiz Rashid]

how to write the code when there are 3 numbers to be proved? for example d1 d2 and d3

Answer 2

[Andrew Newell]

An integer is also a real number, so you only need one test. Also, if you want to delete numbers that are not real, you need to use a tilde (~) for negation. Assuming the input is always numeric, this will work:

x = input('enter the number: ');
if ~isreal(x)
  clear('x');
end

[Andrew Newell]

Judging by the multitude of errors in your short code snippet, I would strongly recommend working through at least one of the MATLAB Tutorials and Learning Resources.

[Shi Yuhao]

The number should meet the two conditions. I don't want to delete it. It's my fault. I want it do again to test it.