Re: [R] How to copy data from data.frame to matrix

From: Dmitrij Kudriavcev <dimitrij.kudriavcev_at_ntsg.lt>
Date: Fri, 04 Mar 2011 21:38:19 +1100

Hello

Let's say, my data.frame is

symbol,day,value

A, 2010-01-01, 0.8888
A, 2010-01-02, 0.6666
B, 2010-01-01, 0.7777

i need to get matrix as

, A, B
2010-01-01, 0.8888, 0.7777
2010-01-02, 0.6666, NA

where A and B is columns name and date used as row name

I found a way how to do it with tapply function, is it a best way (i will need to do this pretty offen and wish to save some time)

Cheers,
Dima

2011/3/4 Ivan Calandra <ivan.calandra_at_uni-hamburg.de>

> Hi,
>
> Let's say your data.frame is called df:
> df <- data.frame(a=rnorm(10), b=rnorm(10))
> data.matrix <- as.matrix(df)
>
> This should work, but be careful with coercion if you have different modes
> in your data.frame
>
> HTH,
> Ivan
>
> PS: next time, provide a reproducible example, using dput() for example
>
> Le 3/4/2011 07:08, Dmitrij Kudriavcev a écrit :
>
>> Hello
>>
>> I'm a new in R
>> I have a large data.frame "s" (this is actualy just a table in mysql) :
>>
>> names(s)
>>>
>> [1] "symbols", "day", "value"
>>
>> I need to convert it to simple matrix. I have define this matrix like
>> this:
>>
>> data.matrix<- matrix(nrow=nDays, ncol=nSymbols, dimnames=list(days,
>>>
>> symbols))
>>
>> then i just copy values to the matrix using for() loop, but it seems to
>> take
>> very long time. Is is a more fast way to do it in R? I know, what i can
>> just
>> gyve s$value as source data to the matrix, but problem is, what for some
>> symbols couple days could be just missed.
>>
>> Cheers,
>> Dima
>>
>> [[alternative HTML version deleted]]
>>
>> ______________________________________________
>> R-help_at_r-project.org mailing list
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>> PLEASE do read the posting guide
>> http://www.R-project.org/posting-guide.html
>> and provide commented, minimal, self-contained, reproducible code.
>>
>>
> --
> Ivan CALANDRA
> PhD Student
> University of Hamburg
> Biozentrum Grindel und Zoologisches Museum
> Abt. Säugetiere
> Martin-Luther-King-Platz 3
> D-20146 Hamburg, GERMANY
> +49(0)40 42838 6231
> ivan.calandra_at_uni-hamburg.de
>
> **********
> http://www.for771.uni-bonn.de
> http://webapp5.rrz.uni-hamburg.de/mammals/eng/1525_8_1.php
>
>
> ______________________________________________
> R-help_at_r-project.org mailing list
> https://stat.ethz.ch/mailman/listinfo/r-help
> PLEASE do read the posting guide
> http://www.R-project.org/posting-guide.html
> and provide commented, minimal, self-contained, reproducible code.
>

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