What is causing the clumping in my piecewise function plot?

[STEMucator]

Homework Statement

Hey there. I'm trying to plot a piecewise function in MATLAB and I'm having some decent success, but there's some things I'm wondering.

Here's the function: http://gyazo.com/d3493a0c13096878acf5a501af8a7f66

Homework Equations

The Attempt at a Solution

My strategy was to create an empty array to hold all the y values since plotting the x values is easy enough. I came up with this short snippet of code:

function plotFunction()
y = []; %Empty array to hold the y values

for i=-40:0.05:30
    if i <= 0
        y(end+1) = 38/11 + sin(i^2);
    elseif i <= 9
        y(end+1) = 38/(11-i);
    else
        y(end+1) = 1.5*sqrt(4*i) + 10;
    end
end

plot(-40:0.05:30, y);
title('Piecewise Function Plot');
xlabel('x-values');
ylabel('y-values');

end

This code yields the following plot, which is really close, but there's something wrong:

http://gyazo.com/1ef70c9ccf6c44f81c14d9915c9edf86

What's with the funky activity near $x = -30$? Why does it get all clumped up around there?

I tried tinkering with the increment of 0.05, but shrinking it clumps the graph together even more.

 

[milesyoung]

What's with the funky activity near $x = -30$? Why does it get all clumped up around there?

It's an artifact of sampling the waveform and plot doing linear interpolation. Try, for instance, to use an increment of 0.001 instead.