From help-octave-request at bevo dot che dot wisc dot edu Thu Jan 16 09:17:50 2003
Subject: Re: newbie question - unsigned conversion
From: Miquel Cabanas <Miquel dot Cabanas at uab dot es>
To: James Ridewood <James dot Ridewood at cern dot ch>
Cc: help-octave at bevo dot che dot wisc dot edu
Date: Thu, 16 Jan 2003 16:17:14 +0100

hi,

On Thu, Jan 16, 2003 at 02:32:52PM +0100, James Ridewood wrote:
>
> x = (0:1:720)';
> data = [x, sin((x-15)*(pi/180)), sin((x-105)*(pi/180)),
> sin((x-135)*(pi/180)), sin((x-225)*(pi/180)), sin((x-255)*(pi/180)),
> sin((x-345)*(pi/180))];

abs_data = abs (data) ;
 
> gplot [0:720] [-1.1:1.1] data with lines, data using 1:2 with lines,
> data
> using 1:3 with lines, data using 1:4 with lines, data using 1:5 with
> lines,
> data using 1:6 with lines, data using 1:7 with lines

then replace "data" with "abs_data" in the gplot command above,
or use

plot (abs_data(:,1), abs_data(:,2:7))

or

plot (x, abs_data(:,2:7))



A cleaner code could be, 

# x axis in degrees up to 720 deg
x = 0:1:720 ;

# phase values in degrees
phase = [-15 -105 -135 -225 -255 -345]
  
# create signals matrix. The code below
# 1) creates a matrix that contains m copies of the x vector,
# where m is the length of the phase vector, i.e. the number
# of phase values "ones (length (phase), 1) * x", then
# 2) creates a matrix that contains n copies of the phase vector,
# where n is the length of the x vector, and transposes it, then
# 3) subtracts the phase matrix from the x matrix, converst from
# degrees to radians, and calculates the sine to obtain the signals
#
# NOTE that there are ways to merge and speed up steps #1 and #2,
# search the internet for "Matlab vectorisation tricks", they also
# apply to Octave.

x_mx = ones (length (phase), 1) * x;
phase_mx = (ones (length (x), 1) * phase)';
signals = sin ((x_mx .- phase_mx).*(pi/180));

# set y-axis range
gset yrange [-1.1:1.1]
plot (x, signals)
fprintf (stdout, "waiting 5 seconds");
pause(5);

# absolute signals
abs_signals = abs (signals);
plot (x, abs_signals)



Miquel


Miquel E Cabanas ------------------------------------------------------
SeRMN, Universitat Autonoma de Barcelona (Miquel dot Cabanas at uab dot es)
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