plotting the graph changing by the range

the given equation is

n=~20
x(n+1)=1.4x(n) for 0<x<0.5
x(n+1)=1.4(1-x(n)) for 0.5<x<1

I tried to use 'if' and 'elseif', but I can't make it repeat.

Answer 1

[Walter Roberson]

x(1) = something
for n = 2 : number of iterations
    if x(n) has some property
        x(n+1) = some formula
    elseif it has some other property
        x(n+1) = some other formula
    else
        give an error because the situation is not defined
    end
end

[Joo Seo Lee]

thanks for the answer, but

x(1) = 0.2
for n = 2 : 20
    if 0<x(n)<0.5
        x(n+1) = 1.4*x(n)
    elseif 0.5<x(n)<1
        x(n+1) = 1.4*(1-x(n))
    else
        give an error because the situation is not defined
    end
end

only is done once and gives an error message that index exceeds the number of array elements.

[Walter Roberson]

In MATLAB,

    if 0<x(n)<0.5

means the same as

    if ((0<x(n))<0.5)

The first test, 0<x(n) gives a logical result that is 0 (false) or 1 (true). Then the second test compares that 0 or 1 to 0.5. That code does not test to see if a variable is in a particular range. To test for a particular range, use seperate tests:

  if 0 < x(n) & x(n) < 0.5

I should have written for

for n = 1 : 20-1