The vectorized approach with logical indexing:
function equation
x = linspace(-5, 30, 200);
m = (x >= 9);
y(m) = 15 * sqrt(4 * x(m)) + 10;
m = (0 <= x & x < 9);
y(m) = 10 * x(m) + 10;
m = (x < 0);
y(m) = 10;
plot(x, y);
end
With a loop:
function equation
x = linspace(-5, 30, 200);
y = zeros(size(x));
for k = 1:numel(x)
if x(k) >= 9
y(k) = 15 * sqrt(4 * x(k)) + 10;
elseif 0 <= x(k) % No need to test x < 9 again!
y(k) = 10 * x(k) + 10;
else % No need to test x(k) again
y(k) = 10;
end
end
plot(x, y)
end
The compact version with logical masking:
function equation
x = linspace(-5, 30, 200);
% Logical mask: Value:
y = (x >= 9) .* (15 * sqrt(4 * x) + 10) + ...
(0 <= x & x < 9) .* (10 * x(idx) + 10) + ...
(x < 0) .* 10;
plot(x, y);
end
Although I assume, that this is a solution of a homework, I do think, that the 3 different approachs are useful to teach Matlab. Please try to understand the differences and do not simply copy&paste one of the codes.
