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Full Discussion: Help with Median
Top Forums UNIX for Dummies Questions & Answers Help with Median Post 302334687 by zajtat on Thursday 16th of July 2009 08:05:39 AM
Old 07-16-2009
Help with Median

Hi,

I know this question has been asked before, but I'd like to ask for some explanation rather than solution regarding finding median in unix.
I've got a simple one column file with over 2 million numbers and I need to find its median. The file looks like this:
0.123
0.235
0.890
0.000 etc (just plain numbers).

The solution that I've found in forum answers was:
1) find the number of lines with this code:

wc -l filename

In my case it is: 2543887

2) if the number is not even (like in my case) than the median can be found with this code:

cat filename| head -$2543887 | tail -1

My question is how head -2543887 is different to head -$2543887? What does the dollar sign do?

Many thanks in advance!
 

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PGASetRealInitPercent(2)					      PGAPack						  PGASetRealInitPercent(2)

NAME
PGASetRealInitPercent - sets the upper and lower bounds for randomly initializing real-valued genes. DESCRIPTION
For each gene these bounds define an interval from which the initial allele value is selected uniformly randomly. With this routine the user specifies a median value and a percent offset for each allele. INPUT PARAMETERS
ctx - context variable median - an array containing the mean value of the interval percent - an array containing the percent offset to add and subtract to the median to define the interval OUTPUT PARAMETERS
none SYNOPSIS
#include "pgapack.h" void PGASetRealInitPercent(ctx, median, percent) PGAContext *ctx double *median double *percent LOCATION
real.c EXAMPLE
Set the initialization routines to select a value for each real-valued gene i uniformly randomly from the interval [i-v,i+v], where $v = i/2$. Assumes all strings are the same length. PGAContext *ctx; double *median, *percent; int i, stringlen; : stringlen = PGAGetStringLength(ctx); median = (double *) malloc(stringlen*sizeof(double)); percent = (double *) malloc(stringlen*sizeof(double)); for(i=0;i<stringlen;i++) { median[i] = (double) i; percent[i] = 0.5; } PGASetRealInitPercent(ctx, median, percent); 05/01/95 PGASetRealInitPercent(2)
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