How do I evaluate a user-input trigonometric function?

2017 11 21
3 个回答
回答已采纳
更新时间：2023 1 8
7 次查看（30 天）

0 个投票

I'm not entirely sure how to explain this but here is the question:
My main issue is I don't know how to use eval when using a user-input trigonometric function. (I don't really need help with the graphing part).
This is my attempt:
n = input('Enter a positive number n: ');
x = linspace(0, n, 1000)
trigfunc = input('Enter a trigonometric function: ', 's');
eval('trigfunc(x)')

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 采纳的回答

Birdman
Birdman 2017-11-21

0 个投票

n=input('enter a pos num\n');
x=linspace(0,n,1000);
trigfunc=input('Enter 1=sin(x), 2=cos(x), 3=tan(x), 4=cot(x)\n');
if(trigfunc==1)
y=sin(x);
plot(x,y);title(['sin(x) from [0 ' ,num2str(n), ']'])
elseif(trigfunc==2)
y=cos(x);
plot(x,y);title(['cos(x) from [0 ' ,num2str(n), ']'])
elseif(trigfunc==3)
y=tan(x);
plot(x,y);title(['tan(x) from [0 ' ,num2str(n), ']'])
elseif(trigfunc==4)
y=cot(x);
plot(x,y);title(['cot(x) from [0 ' ,num2str(n), ']'])
end

更多回答（2 个）

Stephen23
Stephen23 2017-11-21
编辑：Stephen23 2017-11-21

1 个投票

It is simpler to use str2func:
num = str2double(input('End value of vector: ','s'));
fun = str2func(input('Trig function (e.g. sin, cos, etc.): ','s'));
x = linspace(0,num,1000);
y = fun(x);
plot(x,y)
To which it is also easy to add input checking, etc.
Prathap
Prathap 2022-12-26

0 个投票

Plot the trigonometric curve as a function of time. Hint: Use ‘eval’ function within the script to accept different trigonometric functions (e.g., sin, cos, tan, etc.).

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