How to plot exact user defined function?

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Agniswar
Agniswar 2014-3-25
编辑： Serge Boisse 2018-10-27
I have defined a function like this
function z=agni(x)
if x > 0
z=x;
else
z = x.^2;
end
But in the time of plotting plot(x,agni(x)) with x =[-2:.01:2] generate only the curve of x^2. WHY?

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Walter Roberson
Walter Roberson 2014-3-25
if x > 0
means
if all(x > 0)
so if you pass in a vector of x then if any x in the vector is <= 0 then the "if" will not be true.
You should research logical indexing.

更多回答（1 个）

Serge Boisse
Serge Boisse 2018-10-27
编辑：Serge Boisse 2018-10-27
Hello, You should understand that your function accepts a vector of values, not a scalar. then it must return a vector of the same length (that will be plotted) So you may rewrite your function as follows :
function z=agni(x)
z = x; % this is a vector !
ind = (x<0); % logical array : 1 if corresponding element of x is <0
z(ind) = z(ind).^2;
end
Hope this helps. If you prefer to code functions "the classical way", have a look at symbolic functions.

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