How to create a loglog plot out of an array? I have a 2xn array of all my data points called points & my loglog plot is showing the same graph as the normal plot tool.

%the data points match the equation y=x^2 almost exactly and my goal is to create

%the loglog plot with my attempted window. In theory the loglog plot should be a line

%with a slope of two... could be wrong though. 

%Thank you!!

   function
  for i = 1:n
  hold on
  x=points(i,2);
  y=points(i,1);
  plot(x,y,'^','markers',2,'MarkerEdgeColor','b','MarkerFaceColor','y')
  loglog(x,y,'^','markers',2,'MarkerEdgeColor','r','MarkerFaceColor','g')
  xlim([.00001 1])
  ylim([.00001 1])
  end
  end

Answer 1

[Walter Roberson]

When you did the "hold on", you implicitly froze the log vs normal scale of the plot axes, so the loglog() will be treated the same as the plot().

Any one axes only has a single XScale and a single XScale. It is not possible for a single axes to display a plot in normal scale and log scale at the same time. You can use plotyy or the newer yyaxis calls to create two axes, one for each of the scales.

But you need to avoid using "hold on" before loglog() -- that or else you need to

set(gca, 'XScale', 'log', 'YScale', 'log')

which is what loglog() mostly does internally.

[Timothy Corley]

Thank you so much! I would've never guessed that.