From: Robert Klemme <shortcutter@...>
Date: 2013-06-22T02:09:43+09:00
Subject: Re: A question about assignment of multidimensional array error message

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On Fri, Jun 21, 2013 at 6:16 PM, Ruby Student <ruby.student@gmail.com>wrote:

> Team,
>
> The piece of code below is giving me an error which I can't find the
> solution. The assignment below for *
> msgCount[r][c] = mtc *is trwoing an exception. which I list below.
>
> Any suggestions?
>

Yes, a lot.  First of all your Ruby is not very idiomatic.  The smallest
issue is your naming with camelCase which in Ruby land is only used for
class and module names.  All others use snake_case.


> ###################################################################
> #Date      READ     ENTRY    DELETE    ALARM   HOTLIST   SITE     #
> #20130611  2000000  200000   200000    2000    2000      20000    #
> #20130611  2000000  200000   200000    2000    2000      20000    #
> ###################################################################
>

Is this above the file format?  With or without all the hashes?


> msgCount = Array.new            # Empty array. Will have size of [r][7].
> Rows will grow
>
> fn   = "/home/rb/MyData/dp/PR_LOGS/pr_time.log.*"
>
> msgTypes = ["read", "entry", "delete", "alarm", "hotlist", "site"]
>
> fnls = `ls #{fn}`.split         # Create fnls = file names list
>

Don't use backticks for this.  Just use

file_name_list = Dir["/home/rb/MyData/dp/PR_LOGS/pr_time.log.*"]


> fc = fnls.size                  # Number of files to be processed
>
> fnls.each do |f|                # Process each file
>    r = 0                        # Rows are controlled by fnls, number of
> files
>

Do you really want to reset r to 0 for every file?  That will mean that you
will later be overwriting values when you do msgCount[r][c] = mtc.  I don't
think that is what you want.


>    lp,lg,dt = f.split('.')      # this info will be used later
>
>    7.times do |c|               # Process each column
>       mtc = `grep #{msgTypes[c]} #{f} | wc -l`  # Get Message Type Count
>

I am not sure what the line above is supposed to do.  What it currently
_does_ is this: it searches in the current file for all lines containing
the current "message type" and then counts the number of those lines.  Btw,
you can do the counting with "grep -c".

This approach is quite inefficient because it will read each file 7 times.
 Oh wait, and there are only 6 elements in msgType!  One more reason not to
use a number to iterate the array but just use #each as everybody else.


>       *msgCount[r][c] = mtc*
>       r += 1                    # Next row please
>

You are incrementing r 7 * # of  file names.  Is this really what you want?
 Don't you rather want to store counts per file?

   end
> end
>

A more idiomatic way of doing what you are probably trying to do is this:
store counts in nested Hashes based on file name and message type.

msg_types = ["read", "entry", "delete", "alarm", "hotlist", "site"]

line_counts = {}

Dir["/home/rb/MyData/dp/PR_LOGS/pr_time.log.*"].each do |file_name|
# better: ARGV.each do |file_name|
  counts = Hash.new 0

  File.foreach file_name do |line|
    msg_types.each do |mt|
      counts[mt] += 1 if line.include? mt
    end
  end

  line_counts[file_name] = counts
end

# output for testing purposes only
require 'pp'
pp line_counts



> *in `block (2 levels) in <main>': undefined method `[]=' for nil:NilClass
> (NoMethodError)*
>

Joel has explained that already.

Cheers

robert


-- 
remember.guy do |as, often| as.you_can - without end
http://blog.rubybestpractices.com/

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<div dir=3D"ltr"><br><div class=3D"gmail_extra"><br><br><div class=3D"gmail=
_quote">On Fri, Jun 21, 2013 at 6:16 PM, Ruby Student <span dir=3D"ltr">&lt=
;<a href=3D"mailto:ruby.student@gmail.com" target=3D"_blank">ruby.student@g=
mail.com</a>&gt;</span> wrote:<br>
<blockquote class=3D"gmail_quote" style=3D"margin:0px 0px 0px 0.8ex;border-=
left-width:1px;border-left-color:rgb(204,204,204);border-left-style:solid;p=
adding-left:1ex"><div dir=3D"ltr"><div><div>Team,<br><br></div>The piece of=
 code below is giving me an error which I can&#39;t find the solution. The =
assignment below for <b><br>
msgCount[r][c] =3D mtc </b>is trwoing an exception. which I list below.<br>
<br></div>Any suggestions?<br></div></blockquote><div><br></div><div style>=
Yes, a lot. =A0First of all your Ruby is not very idiomatic. =A0The smalles=
t issue is your naming with camelCase which in Ruby land is only used for c=
lass and module names. =A0All others use snake_case.</div>
<div style>=A0</div><blockquote class=3D"gmail_quote" style=3D"margin:0px 0=
px 0px 0.8ex;border-left-width:1px;border-left-color:rgb(204,204,204);borde=
r-left-style:solid;padding-left:1ex"><div dir=3D"ltr"><div><div><div><div>#=
##################################################################<br>
#Date=A0=A0=A0=A0=A0 READ=A0=A0=A0=A0 ENTRY=A0=A0=A0 DELETE=A0=A0=A0 ALARM=
=A0=A0 HOTLIST=A0=A0 SITE=A0=A0=A0=A0 #<br>#20130611=A0 2000000=A0 200000=
=A0=A0 200000=A0=A0=A0 2000=A0=A0=A0 2000=A0=A0=A0=A0=A0 20000=A0=A0=A0 #<b=
r>
#20130611=A0 2000000=A0 200000=A0=A0 200000=A0=A0=A0 2000=A0=A0=A0 2000=A0=
=A0=A0=A0=A0 20000=A0=A0=A0 #<br>##########################################=
#########################<br></div></div></div></div></div></blockquote><di=
v><br></div><div style>Is this above the file format? =A0With or without al=
l the hashes?</div>
<div style>=A0</div><blockquote class=3D"gmail_quote" style=3D"margin:0px 0=
px 0px 0.8ex;border-left-width:1px;border-left-color:rgb(204,204,204);borde=
r-left-style:solid;padding-left:1ex"><div dir=3D"ltr"><div><div><div><div>m=
sgCount =3D Array.new=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0 # Empty array. Will =
have size of [r][7]. Rows will grow<br>

<br>fn=A0=A0 =3D &quot;/home/rb/MyData/dp/PR_LOGS/pr_time.log.*&quot;<br><b=
r>msgTypes =3D [&quot;read&quot;, &quot;entry&quot;, &quot;delete&quot;, &q=
uot;alarm&quot;, &quot;hotlist&quot;, &quot;site&quot;]<br><br>fnls =3D `ls=
 #{fn}`.split=A0=A0=A0=A0=A0=A0=A0=A0 # Create fnls =3D file names list<br>
</div></div></div></div></div></blockquote><div><br></div><div style>Don&#3=
9;t use backticks for this. =A0Just use</div><div style><br></div><div styl=
e>file_name_list =3D Dir[&quot;/home/rb/MyData/dp/PR_LOGS/pr_time.log.*&quo=
t;]</div>
<div>=A0</div><blockquote class=3D"gmail_quote" style=3D"margin:0px 0px 0px=
 0.8ex;border-left-width:1px;border-left-color:rgb(204,204,204);border-left=
-style:solid;padding-left:1ex"><div dir=3D"ltr"><div><div><div><div>
fc =3D fnls.size=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0 # Numbe=
r of files to be processed<br><br>fnls.each do |f|=A0=A0=A0=A0=A0=A0=A0=A0=
=A0=A0=A0=A0=A0=A0=A0 # Process each file<br>=A0=A0 r =3D 0=A0=A0=A0=A0=A0=
=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0 # Rows are controlle=
d by fnls, number of files<br></div></div>
</div></div></div></blockquote><div><br></div><div style>Do you really want=
 to reset r to 0 for every file? =A0That will mean that you will later be o=
verwriting values when you do msgCount[r][c] =3D mtc. =A0I don&#39;t think =
that is what you want.</div>
<div style>=A0</div><blockquote class=3D"gmail_quote" style=3D"margin:0px 0=
px 0px 0.8ex;border-left-width:1px;border-left-color:rgb(204,204,204);borde=
r-left-style:solid;padding-left:1ex"><div dir=3D"ltr"><div><div><div><div>=
=A0=A0 lp,lg,dt =3D f.split(&#39;.&#39;)=A0=A0=A0=A0=A0 # this info will be=
 used later<br>

<br>=A0=A0 7.times do |c|=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0 # Proce=
ss each column<br>=A0=A0=A0=A0=A0 mtc =3D `grep #{msgTypes[c]} #{f} | wc -l=
`=A0 # Get Message Type Count<br></div></div></div></div></div></blockquote=
><div><br></div><div>I am not sure what the line above is supposed to do. =
=A0What it currently _does_ is this: it searches in the current file for al=
l lines containing the current &quot;message type&quot; and then counts the=
 number of those lines. =A0Btw, you can do the counting with &quot;grep -c&=
quot;.</div>
<div><br></div><div style>This approach is quite inefficient because it wil=
l read each file 7 times. =A0Oh wait, and there are only 6 elements in msgT=
ype! =A0One more reason not to use a number to iterate the array but just u=
se #each as everybody else.</div>
<div>=A0</div><blockquote class=3D"gmail_quote" style=3D"margin:0px 0px 0px=
 0.8ex;border-left-width:1px;border-left-color:rgb(204,204,204);border-left=
-style:solid;padding-left:1ex"><div dir=3D"ltr"><div><div><div><div>=A0=A0=
=A0=A0=A0 <b>msgCount[r][c] =3D mtc</b><br>
=A0=A0=A0=A0=A0 r +=3D 1=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=
=A0=A0 # Next row please<br></div></div></div></div></div></blockquote><div=
><br></div><div style>You are incrementing r 7 * # of =A0file names. =A0Is =
this really what you want? =A0Don&#39;t you rather want to store counts per=
 file?</div>
<div style><br></div><blockquote class=3D"gmail_quote" style=3D"margin:0px =
0px 0px 0.8ex;border-left-width:1px;border-left-color:rgb(204,204,204);bord=
er-left-style:solid;padding-left:1ex"><div dir=3D"ltr"><div><div><div><div>
=A0=A0 end<br>end<br></div></div></div></div></div></blockquote><div><br></=
div><div style>A more idiomatic way of doing what you are probably trying t=
o do is this: store counts in nested Hashes based on file name and message =
type.</div>
<div style><br></div><div style><div>msg_types =3D [&quot;read&quot;, &quot=
;entry&quot;, &quot;delete&quot;, &quot;alarm&quot;, &quot;hotlist&quot;, &=
quot;site&quot;]</div><div><br></div><div>line_counts =3D {}</div><div><br>
</div><div>Dir[&quot;/home/rb/MyData/dp/PR_LOGS/pr_time.log.*&quot;].each d=
o |file_name|</div><div># better: ARGV.each do |file_name|</div><div>=A0 co=
unts =3D Hash.new 0</div><div><br></div><div>=A0 File.foreach file_name do =
|line|</div>
<div>=A0 =A0 msg_types.each do |mt|</div><div>=A0 =A0 =A0 counts[mt] +=3D 1=
 if line.include? mt</div><div>=A0 =A0 end</div><div>=A0 end</div><div><br>=
</div><div>=A0 line_counts[file_name] =3D counts</div><div>end</div><div><b=
r></div><div># output for testing purposes only</div>
<div>require &#39;pp&#39;</div><div>pp line_counts</div><div><br></div></di=
v><div>=A0</div><blockquote class=3D"gmail_quote" style=3D"margin:0px 0px 0=
px 0.8ex;border-left-width:1px;border-left-color:rgb(204,204,204);border-le=
ft-style:solid;padding-left:1ex">
<div dir=3D"ltr"><b>in `block (2 levels) in &lt;main&gt;&#39;: undefined me=
thod `[]=3D&#39; for nil:NilClass (NoMethodError)</b><br></div></blockquote=
></div><br>Joel has explained that already.</div><div class=3D"gmail_extra"=
><br>
</div><div class=3D"gmail_extra">Cheers</div><div class=3D"gmail_extra"><br=
></div><div class=3D"gmail_extra">robert<br><br clear=3D"all"><div><br></di=
v>-- <br>remember.guy do |as, often| as.you_can - without end<br><a href=3D=
"http://blog.rubybestpractices.com/">http://blog.rubybestpractices.com/</a>
</div></div>

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