Question

Please use MATLAB.

Write a program to plot the piecewise function using IF statements and a FOR loop in MatLab. Use x as the input vector.

Plot from -20<=x<=20, increment of 1.  

y =   4 x + 10 ,             ? ≥ 9,  

                y =      5? + 5,                   0 ≤ ? < 9,   

                y =     ?² + 6? + 8, ? < 0

Plot each segment of the fn with different shaped points and a different color, for example, blue squares, cyan stars, red plus signs.  

Use a FOR loop with IF statements to fill in the x vector.  Do not define x as x=-20:1:20.

Answer 1

Code:

k = 1;
for j=-20:20
    x(k) = j;
    k = k+1;
end

for i=1:numel(x)
  if x(i) < 0
    y(i) = (x(i))^2 + 6*x(i) + 8;
  elseif (x(i) >= 0) && (x(i) < 9)
    y(i) = 5*x(i) + 5;
  elseif x(i) >= 9
    y(i) = 4*x(i) + 10;
  end
end

% extracting piecewise values of x and y to plot with different markers
x1 = x(1:20); y1 = y(1:20);
x2 = x(21:29); y2 = y(21:29);
x3 = x(30:41); y3 = y(30:41);

plot(x1,y1,'-s','MarkerSize',10,...
    'MarkerEdgeColor', 'blue')
hold on
plot(x2,y2,'-*','MarkerSize',10,...
    'MarkerEdgeColor', 'cyan')
plot(x3,y3,'-+','MarkerSize',10,...
    'MarkerEdgeColor', 'red')
hold off

(Feel free to throw an upvote or comment below if you have any doubts)