add error for when input is not integer

strStart = ["first";"second";"third";"fourth";"fifth";...
    "sixth";"seventh";"eighth";"ninth";"tenth";"eleventh";"twelfth"];
strVerse = ["A partridge in a Pear Tree";"2 Turtle Doves";"3 French Hens"...
    ;"4 Colly Birds";"5 Gold Rings";"6 Geese-a-Laying";"7 Swans-a-Swimming";...
    "8 Maids-a-Milking";"9 Ladies Dancing";"10 Lords-a-Leaping";...
    "11 Pipers Piping";"12 Drummers Drumming";];          
value = input ("Please enter value in the range (1-12):");
while( value > 12 || value < 1 )
    value = input("Error!, Please enter value in the range (1-12): ");
end
fprintf("\nOn the %s day of Christmas\nMy true love gave to me\n",...
    strtrim(strStart(value,1:end)));
while(value ~= 0)
    fprintf("%s\n" , strVerse(value,1:end));
    value = value - 1;
end

I want to add an error message for when the input is not an integer and idk how. also how do i make it so the solution displays output at the center of the user screen?

Answer 1

[Image Analyst]

uiwait(errordlg('Error!  You must enter an integer (a numerical digit)'));

Answer 2

[Walter Roberson]

~isnumeric(value) || mod(value, 1) ~= 0

Answer 3

[Adam Danz]

> I want to add an error message for when the input is not an integer

This returns true when the value is an interger mod(value,1)==0

But you should also test that the value is numerica and a scalar.

isscalar(value) && isnumeric(value) && mod(value,1)~=0)

If you want to repeat the input prompt if the users does not enter an expected response, you can wrap the call to input within a while loop. That's demonstrated in this answer.

> how do i make it so the solution displays output at the center of the user screen

You'll have to use a dialog box such as the one Image Analyst suggested or

h=msgbox(__);
movegui(h,'center')

The last line moves the figure to the center of the screen.