R help - Nov 2005 - Counting the occurence of each unique "charecter string"

LS,
  
  I would really like to know how to count the frequency/occurrence of 
chachters inside a dataset. I am working with extreemly large datasets  of
forest inventory data with a large variety of different species  inside it.
  Each row inside the dataframe represents one individual tree and the
simplified dataframe looks something like this:
  
  num species dbh   
  1        sp1           30
  2        sp1          20
  3        sp2          30
  4        sp1          40
  
  I need to be able to count the number of individuals per species, so I  need a
command that will return for each unique species its occurence  inside the
dataframe;
  
  [sp1]     3
  [sp2]     1
  
  After a long search through help.search() and the web I found very  little and
any alternative like exporting the dataset to another  program(excel) is not
really an option because the dataset is far to  large.
  
  I am using R 2.2.0 in Windows and if anyone knows a solution please help!
  
  Many sincere thanks in advance,
  
  Marco 
  
  
  
		
---------------------------------

	[[alternative HTML version deleted]]

use table() to get what you want.
see ?table

======= 2005-11-28 01:49:19 伳侜佋佢伬伌佇伵佒佇佇伌伒伬仯伜======
>LS,
>  
>  I would really like to know how to count the frequency/occurrence of 
chachters inside a dataset. I am working with extreemly large datasets  of
forest inventory data with a large variety of different species  inside it.
>  Each row inside the dataframe represents one individual tree and the
simplified dataframe looks something like this:
>  
>  num species dbh   
>  1        sp1           30
>  2        sp1          20
>  3        sp2          30
>  4        sp1          40
>  
>  I need to be able to count the number of individuals per species, so I 
need a command that will return for each unique species its occurence  inside
the dataframe;
>  
>  [sp1]     3
>  [sp2]     1
>  
>  After a long search through help.search() and the web I found very  little
and any alternative like exporting the dataset to another  program(excel) is not
really an option because the dataset is far to  large.
>  
>  I am using R 2.2.0 in Windows and if anyone knows a solution please help!
>  
>  Many sincere thanks in advance,
>  
>  Marco 
>  
>  
>  
>		
>---------------------------------
>
>	[[alternative HTML version deleted]]
>
>______________________________________________
>R-help at stat.math.ethz.ch mailing list
>https://stat.ethz.ch/mailman/listinfo/r-help
>PLEASE do read the posting guide!
http://www.R-project.org/posting-guide.html
= = = = = = = = = = = = = = = = = = = 			


 

2005-11-28

------
Deparment of Sociology
Fudan University

My new mail addres is ronggui.huang at gmail.com
Blog:http://sociology.yculblog.com

?table

table(mydata$species)

Marco Visser wrote:
> LS,
>   
>   I would really like to know how to count the frequency/occurrence of 
chachters inside a dataset. I am working with extreemly large datasets  of
forest inventory data with a large variety of different species  inside it.
>   Each row inside the dataframe represents one individual tree and the
simplified dataframe looks something like this:
>   
>   num species dbh   
>   1        sp1           30
>   2        sp1          20
>   3        sp2          30
>   4        sp1          40
>   
>   I need to be able to count the number of individuals per species, so I 
need a command that will return for each unique species its occurence  inside
the dataframe;
>   
>   [sp1]     3
>   [sp2]     1
>   
>   After a long search through help.search() and the web I found very 
little and any alternative like exporting the dataset to another  program(excel)
is not really an option because the dataset is far to  large.
>   
>   I am using R 2.2.0 in Windows and if anyone knows a solution please help!
>   
>   Many sincere thanks in advance,
>   
>   Marco 
>   
>   
>   
> 		
> ---------------------------------
> 
> 	[[alternative HTML version deleted]]
> 
> ______________________________________________
> R-help at stat.math.ethz.ch mailing list
> https://stat.ethz.ch/mailman/listinfo/r-help
> PLEASE do read the posting guide!
http://www.R-project.org/posting-guide.html
> 
-- 
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New York, NY 10010
tel: (212) 845-4495 (Tu, Th)
tel: (732) 452-1424 (M, W, F)
fax: (917) 438-0894

On 27-Nov-05 Marco Visser wrote:
> LS,
>   
>   I would really like to know how to count the frequency/occurrence of 
> chachters inside a dataset. I am working with extreemly large datasets 
> of forest inventory data with a large variety of different species 
> inside it. 
>   Each row inside the dataframe represents one individual tree and the
> simplified dataframe looks something like this:
>   
>   num species dbh   
>   1        sp1           30
>   2        sp1          20
>   3        sp2          30
>   4        sp1          40
>   
>   I need to be able to count the number of individuals per species, so
> I  need a command that will return for each unique species its
> occurence  inside the dataframe; 
>   
>   [sp1]     3
>   [sp2]     1
Does the following help? (Using an artificial example a bit more
complicated than yours). The dataframe "trees" consists of a list
of species names under "Species", and values of a numeric variable
under "X".


  > trees
              Species   X
  1     Larix decidua 203
  2  Pinus sylvestris 303
  3     Larix decidua 202
  4  Pinus sylvestris 301
  5       Picea abies 102
  6       Picea abies 103
  7  Pinus sylvestris 302
  8       Picea abies 101
  9     Larix decidua 201
  10      Picea abies 104
  11      Picea abies 105
  12 Pinus sylvestris 304


  > freqs<-as.data.frame(table(trees$Species))
  > colnames(freqs)<-c("Species","Counts")
  > freqs
             Species Counts
  1    Larix decidua      3
  2      Picea abies      5
  3 Pinus sylvestris      4


  > mean(freqs$Counts)
  [1] 4
  > sd(freqs$Counts)
  [1] 1


Just using table() would give you the same information, but
converting it to a dataframe makes that information more
readily accessible by familiar methods.

Hoping this helps,
Ted.


--------------------------------------------------------------------
E-Mail: (Ted Harding) <Ted.Harding at nessie.mcc.ac.uk>
Fax-to-email: +44 (0)870 094 0861
Date: 27-Nov-05                                       Time: 18:27:10
------------------------------ XFMail ------------------------------

On 11/27/05, Ted Harding <Ted.Harding at nessie.mcc.ac.uk>
wrote:
> On 27-Nov-05 Marco Visser wrote:
> > LS,
> >
> >   I would really like to know how to count the frequency/occurrence of
> > chachters inside a dataset. I am working with extreemly large datasets
> > of forest inventory data with a large variety of different species
> > inside it.
> >   Each row inside the dataframe represents one individual tree and the
> > simplified dataframe looks something like this:
> >
> >   num species dbh
> >   1        sp1           30
> >   2        sp1          20
> >   3        sp2          30
> >   4        sp1          40
> >
> >   I need to be able to count the number of individuals per species, so
> > I  need a command that will return for each unique species its
> > occurence  inside the dataframe;
> >
> >   [sp1]     3
> >   [sp2]     1
>
> Does the following help? (Using an artificial example a bit more
> complicated than yours). The dataframe "trees" consists of a list
> of species names under "Species", and values of a numeric
variable
> under "X".
>
>
>  > trees
>              Species   X
>  1     Larix decidua 203
>  2  Pinus sylvestris 303
>  3     Larix decidua 202
>  4  Pinus sylvestris 301
>  5       Picea abies 102
>  6       Picea abies 103
>  7  Pinus sylvestris 302
>  8       Picea abies 101
>  9     Larix decidua 201
>  10      Picea abies 104
>  11      Picea abies 105
>  12 Pinus sylvestris 304
>
>
>  > freqs<-as.data.frame(table(trees$Species))
>  > colnames(freqs)<-c("Species","Counts")
>  > freqs
>             Species Counts
>  1    Larix decidua      3
>  2      Picea abies      5
>  3 Pinus sylvestris      4
>
>
>  > mean(freqs$Counts)
>  [1] 4
>  > sd(freqs$Counts)
>  [1] 1
>
>
> Just using table() would give you the same information, but
> converting it to a dataframe makes that information more
> readily accessible by familiar methods.
>
> Hoping this helps,
> Ted.
>
>
or using the iris dataset that comes with R and making use
of as.data.frame.table we can shorten that slightly to just:

as.data.frame.table(table(Species = iris$Species), responseName =
"Count")

Incidently, I just noticed that there is an inconsistency between as.data.frame
and as.data.frame.table making it impossible to shorten as.data.frame.table
to as.data.frame in the above due to the responseName= argument
which is not referenced in the generic.
> args(as.data.frame)
function (x, row.names = NULL, optional = FALSE)
NULL
> args(as.data.frame.table)
function (x, row.names = NULL, optional = FALSE, responseName =
"Freq")
NULL
> R.version.string # Windows
[1] "R version 2.2.0, 2005-10-24"