bash prepare file for gnuplot calculate value in second row

Question

I want to plot box chart form file with has data already in two columns. Catch is that second column is in hex and need be additionality multiple by some const (734) i.e test.dat

amp 0x223 
dupa 0x333
jasiu 0x4a4
halo 0xb1

best will be to do that in bash one liner . I just end with this

cat test.dat |xargs printf '%s $(printf "scale=2; %d/734\\n" | bc)\n' |xargs -0 echo

but that print some things like that

amp $(printf "scale=2; 547/734\n" | bc)
dupa $(printf "scale=2; 819/734\n" | bc)
jasiu $(printf "scale=2; 1188/734\n" | bc)
halo $(printf "scale=2; 177/734\n" | bc)

and not calculating second value. Last echo should do the work but is not doing , why and how to fix this ?

Please provide a complete example! Where is anything related to gnuplot ? — Mark Setchell
– Mark Setchell, Commented Mar 1, 2018 at 22:04
I made mistake in description , value have to be divided by const not multiply , and result should be with precision of two places after dot/coma — Sebastian Mikulski
– Sebastian Mikulski, Commented Mar 2, 2018 at 6:46

karakfa · Accepted Answer · 2018-03-01 22:46:30Z

2

awk to the rescue!

$ awk -P '{printf("%s %d\n", $1, $2*734)}' file

amp 401498
dupa 601146
jasiu 871992
halo 129918

convert 2nd field to decimal and multiply with 734. -P is for POSIX mode, may disable many other useful features, however here anything else is not needed.

answered Mar 1, 2018 at 22:46

karakfa

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2 Comments

Sebastian Mikulski Over a year ago

Yes , it is what is in description , but I made mistake in description should be "...additionality divided by some const " additionally with precision of two places after dot/coma with is done in my script by printf "scale=2; 547/734\n" | bc. Of courese Your solution is what is currently in description and thanks for that, this is some clue

Mark Setchell Over a year ago

@SebastianMikulski Just change * to / and %d to %.2f

Mark Setchell · Accepted Answer · 2018-03-02 09:55:39Z

1

Some late night fun...

Perl to the rescue! ;-)

perl -aE 'say $F[0] . " " . hex($F[1])/734' file

edited Mar 2, 2018 at 9:55

answered Mar 1, 2018 at 23:44

Mark Setchell

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Comments

Christoph · Accepted Answer · 2018-03-04 10:38:20Z

1

gnuplot to the rescue!

plot "test.dat" using 0:($2/734.0):xtic(1) with boxes

edited Mar 4, 2018 at 10:38

answered Mar 4, 2018 at 8:15

Christoph

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1 Comment

Christoph Over a year ago

@MarkSetchell Just found out, that gnuplot parses the hex data correctly without any hacks.

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