1 files changed, 37 insertions, 6 deletions
diff --git a/macros/decimate.sci b/macros/decimate.sci
index 5a2e428..9f8aeb5 100644
--- a/macros/decimate.sci
+++ b/macros/decimate.sci
@@ -1,14 +1,47 @@
 function y = decimate(x, q, n, ftype)
+//Decimation — decrease sample rate by integer factor
+
+//Calling Sequence
+//y = decimate(x,q)
+//y = decimate(x,q,n)
+// y = decimate (…, "fir")
+
+//Parameters
+//x: input sequence
+//q: reduction factor
+//n : filter order
+//ftype: filter type : iir or fir
+
+//Description
+//this is an octave function
+//y = decimate(x,q) reduces the sample rate of x, the input signal, by a factor of q.
+//By default, an order n Chebyshev type I filter is used. If n is not specified, the default is 8.
+//If the optional argument "fir" is given, an order n FIR filter is used, with a default order of 30 if n is not given.
+//Note that q must be an integer for this rate change method.
+//
+//Example :
+//t = 0:.00025:1;
+//x = sin(2*%pi*30*t) + sin(2*%pi*60*t);
+//y = decimate(x,4);
+//subplot(211);
+//plot2d3((0:120),x(1:121));
+//subplot(212);
+//plot2d3((0:30),y(1:31));
+
+//This will result in plots of original sequence v/s sample number and decimated sequence v/s sample number
+
 rhs = argn(2)
 if(rhs<2 | rhs>4)
 error("Wrong number of input arguments.")
 elseif(~(sum(length(q)==1) & q == fix (q) & q > 0))
 error("Parameter 2 must be a positive integer.")
 end
-if (nargin < 3)
+//if (nargin < 3)
+if(argn(2) < 3)
 ftype = "iir"
 n = []
-elseif (nargin < 4)
+//elseif (nargin < 4)
+elseif(argn(2) < 4)
 if (ischar (n))
 ftype = n
 n = []
@@ -17,7 +50,8 @@ ftype = "iir"
 end
 end
 
-if (~ and(strcmp (ftype, {"fir", "iir"})))
+//if (~ and(strcmp (ftype, {"fir", "iir"})))    // if strings are equal strcmp returns 0
+if(strcmp(ftype,"iir") & strcmp(ftype,"fir"))
 error("Filter type must be either fir or iir.")
 end
 
@@ -42,6 +76,3 @@ case 4 then
 y = callOctave("decimate", x, q, n, ftype)
 end
 endfunction
-
-
-