Plot x and y with two function

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Dani D
Dani D 2016-4-25
编辑： Star Strider 2016-4-25
Hello, I want plot x and y , but i can't
x = rand(65000,1);
if x <= 0.5
y = sqrt(x);
elseif x > 0.5
y = x^1.25;
end
plot(x,y);

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回答（1 个）

Star Strider
Star Strider 2016-4-25
I am not certain what you are doing with ‘x’ being random, but this will work:
x = rand(65000,1);
y = (x <= 0.5).*(sqrt(x)) + (x > 0.5).*(x.^1.25);
figure(1)
plot(x, y)
grid
  2 个评论
Dani D
Dani D 2016-4-25
No , I have if else. If less or equal 0.5 we have sqrt(x) else if greater than 0.5 we have x^1.25
Star Strider
Star Strider 2016-4-25
编辑：Star Strider 2016-4-25
That is what my code does. It uses logical index ‘masking’ instead of an if block.
The logical mask is equal to 1 where the logical condition is true (and is multiplied by the value of the function at that value of ‘x’) and 0 where the logical condition is false, so the value for that particular condition would be 0. The code for ‘y’ adds the two conditions together with respect to their function values over each condition to create a continuous vector.
EDIT — This is a much less efficient way of doing it, but it produces the same result:
x = rand(65000,1);
for k1 = 1:length(x)
if x(k1) <= 0.5
y(k1) = sqrt(x(k1));
elseif x(k1) > 0.5
y(k1) = x(k1)^1.25;
end
end
plot(x,y);

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