Help with using a switch statement

Question

Marina Christakos 2019-1-23

0
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此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/441154-help-with-using-a-switch-statement

编辑： Stephen23 2019-1-23

Screen Shot 2019-01-23 at 3.34.33 PM.png

I was supposed to write a code that asks for a letter and a number. If the variables 'c', 't', or 's' were entered, it should find the cosine, tangent, or sine of the entered number. (also had to use a switch statement). When I run my code it asks for the number and letter but doesn't compute anything. How would I change my code to actually compute the value of the entered number?

q = input('enter number');
letter = input('enter letter');
't' == 'tangent';
'c' == 'cosine';
's' == 'sine';
switch letter
    case {'s'}
        letter = 's';
        disp(sine(q));
    case {'c'}
        letter = 'c';
        disp(cosine(q));
    case {'t'}
        letter = 't';
        disp(tangent(q));
    otherwise
        letter = 'unknown';
end

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Answer 1

Stephen23 2019-1-23

0
链接

此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/441154-help-with-using-a-switch-statement#answer_357746

编辑：Stephen23 2019-1-23

在 MATLAB Online 中打开

val = str2double(input('enter number','s'));
chr = input('enter letter','s');
switch chr
    case 's'
        disp(sin(val))
    case 'c'
        disp(cos(val))
    case 't'
        disp(tan(val))
    otherwise
        error('oh no!')
end

A simple internet search would have quickly shown you the correct functions for calculating the sine, cosine, and tangent. Reading the documentation is much more reliable than guessing.

Note that all of your lines with == do nothing: e.g. the line

't' == 'tangent';

performs an element-wise comparison of the characters in the character vector 'tangent' with the single character 't'. Without even running that code I can tell you that the output will be:

[1,0,0,0,0,0,1]

because only the first and last characters are t's. In any case, you do not allocate this logical vector to anything, or use it in any way, so it is simply discarded. Ditto all the other == lines.