MATLAB Programming/Loglog

Introduction

The loglog command plots both x and y data sets on a log scale while the plot command plots both axes on linear scales and the semilogx/y command plots 1 axis on a linear scale and the other axis on a log scale. Other than the scale of the axes, the 3 plotting commands are identical in most ways.

Basic Usage

The basic usage of the plot, semilogx/y, and loglog command are identical. Below is an example of how a PSD would be plotted

  >> Fs = 1000;                              % Sample Rate of 1 kHz
  >> t = 0:(1/Fs):1000;                      % Time vector
  >> x = sin(pi*t);                          % Sine wave based on time vector
  >> [Pxx, f] = pwelch(x, [], [], [], Fs);
  >> loglog(f, Pxx)
  >> grid on
  >> xlabel('Frequency (Hz)')
  >> ylabel('Magnitude (units^2/Hz)')
  >> title('PSD of Sine Wave')

See Also

• pwelch

External Links

• ControlTheoryPr.com page on loglog