# Produce the same result but without using a for-loop.

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laith awwad on 6 Apr 2021
Edited: Walter Roberson on 6 Apr 2021
% Produce the same result but without using a for-loop.
% Increment
dx = 35/300;
% Independent variable
x = -5:dx:30; % x = linspace(-5,30,300)
for n = 1:length(x)
if x(n) >= 9
y(n) = 15*sqrt(4*x(n)) + 10;
elseif (x(n) >= 0) && (x(n) <= 9)
y(n) = 10*x(n) + 10;
else
y(n) = 10;
end
end
plot(x,y), xlabel('x'), ylabel('y'), grid on
Rik on 6 Apr 2021

Cris LaPierre on 6 Apr 2021
Edited: Cris LaPierre on 6 Apr 2021
This is a piecewise function. Perhaps the easiest way to do this is using the piecewise function.
If your assignment doesn't allow that, then create 3 vectors, one for each equation, and solve each for all values of x. Then multiply each by a logical array created from x and the corresponding conditional statement(s). Finally, add all three vectors together.
See Ch 12 of MATLAB Onramp if you need help creating the logical array, and Ch 6 if you need help on elementwise multiplication.
laith awwad on 6 Apr 2021
it worked you helped me alot thank you soooo much

Walter Roberson on 6 Apr 2021
syms y(x)
y(x) = piecewise(x>=9, 15*sqrt(4*x)+10, 0>=x=<9, 10*x+10,10)
^^
MATLAB does not have an =< operator; it has a <= operator.
dx = 35/300;
xvalue = -5:dx:30;
fplot(y)
fplot() by default plots from -5 to +5 . Your assignment to xvalue does not affect that. To have it plot over a different interval, the interval would have to be passed as the second parameter, such as
fplot(y, [-5, 30])
Only the endpoints of the interval would be passed.
fplot() always chooses its own points to plot at. If you only want to plot at particular points, you should not use fplot(); you should use plot() instead.
plot() does not accept formulas, so you would need to
plot(xvalue, y(xvalue))
laith awwad on 6 Apr 2021
it worked thank you so much