Find Where Values Change From Positive To Negative and viceversa Post: 302503775

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Top Forums Shell Programming and Scripting Find Where Values Change From Positive To Negative and viceversa Post 302503775 by malandisa on Friday 11th of March 2011 03:44:49 PM

03-11-2011

Registered User

Find Where Values Change From Positive To Negative and viceversa

Hi all,

I have a file that looks like shown below. I want to find places where the value in column 2 change from negative to positive and vice versa and return the value on column 1 at that point. I wonder if this is possible in shell script or awk .. please help!

Here is the original data

Quote:

2.91 -1.19 1.34 78.00 2.00
3.09 -1.21 1.33 91.00 2.00
3.28 -1.03 1.41 87.00 2.00
3.47 -0.78 1.48 86.00 2.00
3.66 -0.47 1.51 86.00 2.00
3.84 0.01 1.42 88.00 2.00
4.03 0.47 1.15 85.00 2.00
4.22 0.93 0.45 87.00 2.00
4.41 1.00 0.00 87.00 1.00
4.59 1.00 0.00 87.00 1.00
4.78 1.00 0.00 87.00 1.00
4.97 1.00 0.00 84.00 1.00
5.16 1.00 0.00 88.00 1.00
5.34 1.00 0.00 86.00 1.00
8.53 1.00 0.00 86.00 1.00
8.72 1.00 0.00 87.00 1.00
8.91 1.00 0.00 78.00 1.00
9.09 1.00 0.00 91.00 1.00
9.28 1.00 0.00 87.00 1.00
9.47 1.00 0.00 86.00 1.00
9.66 1.00 0.00 86.00 1.00
9.84 1.00 0.00 88.00 1.00
10.03 0.54 1.09 85.00 2.00
10.22 -0.86 1.46 87.00 2.00
10.41 -1.86 0.63 87.00 2.00
10.59 -1.76 0.82 87.00 2.00
10.78 -0.83 1.47 87.00 2.00
10.97 0.07 1.40 84.00 2.00
11.16 0.80 0.76 88.00 2.00
11.34 1.00 0.00 86.00 1.00

And the desired output is

Quote:

3.66
10.03
10.78

Is there a way I can do this? And sorry I am a real newbie in shell scripting and I have no clue how to start this and so I have no suggested code

Thank you very much for your assistance and advice
Malandisa

malandisa

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ppmtopgm

ppmtopgm(1)						      General Commands Manual						       ppmtopgm(1)

NAME

       ppmtopgm - convert a portable pixmap into a portable graymap

SYNOPSIS

       ppmtopgm [ppmfile]

DESCRIPTION

       Reads  a  portable  pixmap  as  input.  Produces a portable graymap as output.  The output is a "black and white" rendering of the original
       image, as in a black and white photograph.  The quantization formula used is .299 r + .587 g + .114 b.

       Note that although there is a pgmtoppm program, it is not necessary for simple conversions from pgm to ppm , because any  ppm  program  can
       read  pgm  (and	pbm  ) files automatically.  pgmtoppm is for colorizing a pgm file.  Also, see ppmtorgb3 for a different way of converting
       color to gray.  And ppmdist generates a grayscale image from a color image, but in a way that makes it easy to differentiate  the  original
       colors, not necessarily a way that looks like a black and white photograph.

QUOTE

       Cold-hearted orb that rules the night
       Removes the colors from our sight
       Red is gray, and yellow white
       But we decide which is right
       And which is a quantization error.

SEE ALSO

       pgmtoppm(1),ppmtorgb3(1),rgb3toppm(1),ppmdist(1),ppm(5),pgm(5)

AUTHOR

       Copyright (C) 1989 by Jef Poskanzer.

								   10 April 2000						       ppmtopgm(1)