Matrix dimensions must agree while using if

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Sang Heon Lee
Sang Heon Lee 2017-9-15
编辑： Martin Grden 2020-10-28
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.

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采纳的回答

KSSV
KSSV 2017-9-15
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

更多回答（2 个）

Jan
Jan 2017-9-15
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.
  1 个评论
Martin Grden
Martin Grden 2020-10-28
编辑：Martin Grden 2020-10-28
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')
...

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Arun Kumar Misra
Arun Kumar Misra 2017-9-15
编辑：Arun Kumar Misra 2017-9-15
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

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