learningMatlab

Loop over plots

Find a way to layer plots

Useful operators, commands, and concepts for this unit…

hold(), figure(), clf, for, colormap

Given the following data, find a way to plot a family of curves in the same figure window, for each combination of $\mu$, $\sigma$, and with appropriately coloured lines.

x = linspace(-3,3,100);
mus = [-1, -0.5, 0, +0.5, 1];
sigmas = [0.5, 0.5, 1, 2, 2];
colors = parula(5);

% for one...
y = normcdf(x, mus(1), sigmas(1));
figure
plot(x,y,'color', colors(1,:)); % first in the "family"

Hint 1 - calculate y in loop

Step one in solving this problem could be to figure out how to calculate the ``y`` values in a loop (and worry about the plotting later).


% how many parameters?
nParams = numel(mus); % if we grow the vector this will still work
% now loop from 1...nParams
for iParam = 1:nParams
  y = normcdf(x, mus(iParam), sigmas(iParam));
end

This code picks the first element of ``mus`` and ``sigmas`` on the first iteration, the second on the second iteration, etc. But ``y`` gets over-written each time we go through the loop. That's fine for here, but you could think about how to keep hold on to that information instead.

Hint 2 - plot on top of other stuff

Step two in solving this problem could be to figure out how to plot one thing on top of another...


% how many parameters?
nParams = numel(mus); % if we grow the vector this will still work
figure % make a new figure window
% now loop from 1...nParams
for iParam = 1:nParams
  y = rand( size(x) ); % make something random of correct size
  plot(x, y, 'k'); % k -> black lines
  hold('on'); % make sure you don't erase
  % the following also works...
  % hold on
end

Hint 3 - pick different colors

Step 3 is to pick a different colour each time...


% how many parameters?
nParams = numel(mus);
figure % make a new figure window
for iParam = 1:nParams
  y = rand( size(x) ); % make something random of correct size
  theColor = colors(iParam, :); % pick the i'th row
  plot(x, y, 'color', theColor );
  hold('on'); % make sure you don't erase
  % the following also works...
  % hold on
end

Hint 4 - put it all together


nParams = numel(mus);
figure % make a new figure window
for iParam = 1:nParams
  % make a new y, using consecutive mus and sigmas!
  y = normcdf(x, mus(iParam), sigmas(iParam));
  theColor = colors(iParam, :); % pick the i'th row
  plot(x, y, 'color', theColor );
  hold('on'); % make sure you don't erase
end

Nesting loops - how to loop over loops.

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learningMatlab

Loop over plots

Find a way to layer plots

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