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

loglog plotMATLAB

%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

Best Answer

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.
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