How do I plot an indeterminate number of lines?

I have a common problem where I need to plot a number of lines n, but I don't know how many there will be.

If I am making a series of lines I can do it with a matrix, then just do this:

plot(x scale, y(1), x scale, y(2),...,x scale, y(n))

The problem is that I don't always know what n will be, so I have to do it like this:

for i=1:1:n
plot(x scale, y(i))

The problem is that then the lines are all blue (I'd like the colors to cycle) and I can't make a legend.

Does anyone know how to solve this problem?

[Walter Roberson]

Are those y(1) y(2) and so on all scalar values? So you are plotting a series of horizontal lines ? Or is y(1) y(2) really y{1} y{2} etc., cell array entries?

Answer 1

[Walter Roberson]

http://www.mathworks.com/help/techdoc/ref/hold.html

hold all holds the graph and the current line color and line style so that subsequent plotting commands do not reset the ColorOrder and LineStyleOrder property values to the beginning of the list. Plotting commands continue cycling through the predefined colors and line styles from where the last graph stopped in the list.

Answer 2

[Jan]

n = 32;
map = jet(16);
lineH = zeros(n, 1);
legendC = cell(n, 1);
axes('NextPlot', 'add');  % Equivalent to "hold on"
for i = 1:n
  color      = map(rem(i, 16) + 1, :);
  lineH(i)   = line(1:10, rand(1, 10), 'Color', color);
  legendC{i} = sprintf('Line %d', i);
end

legend(lineH, legendC);

I cannot debug this currently. The low-level function line is faster than the high-level function plot.