Problem multiplying exponential function with negative value
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I want to plot x(t) = t*(e−0.15t), − 20 ≤ t ≤ 20
I've tried:
t = -20:1:20;
x(t) = t.*(exp(-0.15*t));
plot(t,x(t))
采纳的回答
This statement
x(t) = t.*(exp(-0.15*t));
says to set the value of x at indexes given by t to the expression on the right-hand side. Indexes must be positive integers (1, 2, 3, ...), but t has some negative values and a zero value in it, so that's why the error happens.
In fact the syntax for what you want to do is slightly simpler. You can just say:
t = -20:1:20;
% no need to specify indexes into x, just set the whole thing:
x = t.*(exp(-0.15*t));
Then to plot:
plot(t,x)
1 个评论
That makes t and x each vectors. Alternatively, you can make x a function of t if you want, and do the same thing:
x = @(t)t.*(exp(-0.15*t));
In this case the syntax x(t) evaluates the function x at the values of t given in t. Then your original syntax in the plot statement would be correct:
t = -20:1:20;
plot(t,x(t));
更多回答（1 个）
Yongjian Feng
2022-2-11
Try this:
t = -20:1:20;
x_t = t.*(exp(-0.15*t));
plot(t, x_t)
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