How do you multiply the letter "a" by 3?

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Muhendisleksi
Muhendisleksi 2017-9-1
编辑： Stephen23 2017-9-1
a =
'x'
>> a*3
Undefined operator '*' for input arguments of type 'cell'.
The result I want to achieve: 3*x
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Stephen23
Stephen23 2017-9-1
编辑：Stephen23 2017-9-1
Given
a = 'x'
and
>> a*3
Undefined operator '*' for input arguments of type 'cell'.
and the statement "The result I want to achieve: 3*x", what is x supposed to be? Is this a reference to something else?

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回答（4 个）

Jan
Jan 2017-9-1
Perhaps you do not want a symbolic calculation but a string manipulation.
c = {'a'}
b = sprintf('%d%s', 3, c{1});
the cyclist
the cyclist 2017-9-1
编辑：the cyclist 2017-9-1
If you have a character array and you want to replicate it, use repmat:
repmat('a',1,3)
the cyclist
the cyclist 2017-9-1
If you are trying to multiply a symbolic variable, then you should just be able to use mtimes as you have done. But why is your symbolic in a cell array?
Steven Lord
Steven Lord 2017-9-1
Multiplying a cell array by a number is not defined, regardless of what the cell in the cell array contains. So something like 3*{'a'} will error.
Multiplying a char array by a number is defined, but it will not do what you're trying to do. Since the ASCII value of 'a' is 97 (which you can find using the command double('a')) computing 3*'a' returns 291 (= 3*97).
If you have Symbolic Math Toolbox, define a to be a symbolic variable then multiply that symbolic variable by 3 to do what you're trying to do.
syms a
y = 3*a
You can check if you have Symbolic Math Toolbox installed by looking for it in the output of the ver function.

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