Matrix dimensions must agree while using if

 celestialBody = input('Celestial body = ','s');

 if celestialBody == 'moon'
    mass1 = MASS_OF_MOON;
    distance = RADIUS_OF_MOON;

 elseif celestialBody == 'mercury'
    mass1 = MASS_OF_MERCURY;
    distance = RADIUS_OF_MERCURY;
 else
    mass1 = 0;
    distance = 1;  
 end

Above is my script and whenever I run this script, type the celestialBody as mercury, it says

 Matrix dimensions must agree.

 Error in exoweight (line 16)
 if celestialBody == 'moon'

how can I solve this error? the values for the constants are set.

Answer 1

[KSSV]

doc Strcmpi or strcmp

celestialBody = input('Celestial body = ','s');
if strcmpi('moon',celestialBody)
    mass1 = MASS_OF_MOON;
    distance = RADIUS_OF_MOON;
elseif strcmpi('mercury',celestialBody)
    mass1 = MASS_OF_MERCURY;
    distance = RADIUS_OF_MERCURY;
else
    mass1 = 0;
    distance = 1;
end

Answer 2

[Jan]

The problem is in

if celestialBody == 'moon'

The == operator works elementwise. Therefore the strings on the left and the right need to have the same number of elements (or one must be a scalar character). As suggested already, use strcmp or strcmpi to compare strings.

[Martin Grden]

Maybe MATHWORKS should offer a substitute to doing string comparisons, when checking a 2-value property (for ex. timer.Running). For now, you can do:

if (timer.running(end)=='n')

...

Answer 3

[Arun Kumar Misra]

try this it works

celestialBody = input('Celestial body = ','s');

 if strcmp(celestialBody,'moon')
    mass1 = MASS_OF_MOON;
    distance = RADIUS_OF_MOON;
 elseif strcmp(celestialBody,'mercury')
    mass1 = MASS_OF_MERCURY;
    distance = RADIUS_OF_MERCURY;
 else
    mass1 = 0;
    distance = 1;  
 end