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Paul Miller

2013-Apr-09 20:52 UTC

[R] Converting matrix to data frame without losing an assigned dimname

Hello All,

Would like to be able to convert a matrix to a dataframe without losing an
assigned dimname.

Here is an example that should illustrate what I'm talking about.

tableData <- state.x77[c(7, 38, 20, 46), c(7, 1, 8)]
names(dimnames(tableData)) <- c("State", "")
tableData

State          Frost Population  Area
  Connecticut    139       3100  4862
  Pennsylvania   126      11860 44966
  Maryland       101       4122  9891
  Virginia        85       4981 39780

tableData <- as.data.frame(tableData)
tableData

             Frost Population  Area
Connecticut    139       3100  4862
Pennsylvania   126      11860 44966
Maryland       101       4122  9891
Virginia        85       4981 39780

Notice how "State" gets removed when converting to a dataframe. How
can I get a dataframe with a separate column called "State" instead of
having the state become the row.names? I can think of an ugly way to do it but
suspect there must be something more elegant.

Thanks,

Paul

Gabor Grothendieck

2013-Apr-09 21:42 UTC

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[R] Converting matrix to data frame without losing an assigned dimname

On Tue, Apr 9, 2013 at 4:52 PM, Paul Miller <pjmiller_57 at yahoo.com>
wrote:> Hello All,
>
> Would like to be able to convert a matrix to a dataframe without losing an
assigned dimname.
>
> Here is an example that should illustrate what I'm talking about.
>
> tableData <- state.x77[c(7, 38, 20, 46), c(7, 1, 8)]
> names(dimnames(tableData)) <- c("State", "")
> tableData
>
> State          Frost Population  Area
>   Connecticut    139       3100  4862
>   Pennsylvania   126      11860 44966
>   Maryland       101       4122  9891
>   Virginia        85       4981 39780
>
> tableData <- as.data.frame(tableData)
> tableData
>
>              Frost Population  Area
> Connecticut    139       3100  4862
> Pennsylvania   126      11860 44966
> Maryland       101       4122  9891
> Virginia        85       4981 39780
>
> Notice how "State" gets removed when converting to a dataframe.
How can I get a dataframe with a separate column called "State"
instead of having the state become the row.names? I can think of an ugly way to
do it but suspect there must be something more elegant.
>
Try this:
> library(plyr)
> adply(tableData, 1, c)         State Frost Population  Area
1  Connecticut   139       3100  4862
2 Pennsylvania   126      11860 44966
3     Maryland   101       4122  9891
4     Virginia    85       4981 39780

--
Statistics & Software Consulting
GKX Group, GKX Associates Inc.
tel: 1-877-GKX-GROUP
email: ggrothendieck at gmail.com

Rolf Turner

2013-Apr-09 22:24 UTC

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[R] Converting matrix to data frame without losing an assigned dimname

Interesting.  The problem is that only ***arrays*** are allowed to have
a dimnames attribute, and data frames are not arrays (they are lists).

The only way that I can see to achieve the effect that you want is to
make the row names into the first column of your data frame and wipe
out the row names.  That is probably the "ugly" procedure that
you've
already thought of.

You could automate the procedure to some extent:

fixUpRowNames <- function(X,name) {
X <- as.data.frame(X)
X <- cbind(rownames(X),X)
names(X)[1] <- name
rownames(X) <- NULL
X
}

Then do:

tableData <- state.x77[c(7, 38, 20, 46), c(7, 1, 8)]
newTD <- fixUpRowNames(tableData,"State")

And then all is (more or less) in harmony.

Best that I can come up with.

     cheers,

         Rolf Turner

On 04/10/2013 08:52 AM, Paul Miller wrote:> Hello All,
>
> Would like to be able to convert a matrix to a dataframe without losing an
assigned dimname.
>
> Here is an example that should illustrate what I'm talking about.
>
> tableData <- state.x77[c(7, 38, 20, 46), c(7, 1, 8)]
> names(dimnames(tableData)) <- c("State", "")
> tableData
>
> State          Frost Population  Area
>    Connecticut    139       3100  4862
>    Pennsylvania   126      11860 44966
>    Maryland       101       4122  9891
>    Virginia        85       4981 39780
>
> tableData <- as.data.frame(tableData)
> tableData
>
>               Frost Population  Area
> Connecticut    139       3100  4862
> Pennsylvania   126      11860 44966
> Maryland       101       4122  9891
> Virginia        85       4981 39780
>
> Notice how "State" gets removed when converting to a dataframe.
How can I get a dataframe with a separate column called "State"
instead of having the state become the row.names? I can think of an ugly way to
do it but suspect there must be something more elegant.

arun

2013-Apr-09 23:00 UTC

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[R] Converting matrix to data frame without losing an assigned dimname

Hi,

library(plyr)
library(reshape2)
?df2<-mutate(dcast(melt(tableData),State~Var2),
State=factor(State,levels=rownames(tableData)))
dfNew<-df2[as.numeric(df2$State),c(1,3:4,2)]
dfNew$State<- as.character(dfNew$State)
?dfNew
#???????? State Frost Population? Area
#1? Connecticut?? 139?????? 3100? 4862
#3 Pennsylvania?? 126????? 11860 44966
#2???? Maryland?? 101?????? 4122? 9891
#4???? Virginia??? 85?????? 4981 39780
A.K.




----- Original Message -----
From: Paul Miller <pjmiller_57 at yahoo.com>
To: r-help at r-project.org
Cc: 
Sent: Tuesday, April 9, 2013 4:52 PM
Subject: [R] Converting matrix to data frame without losing an assigned dimname

Hello All,

Would like to be able to convert a matrix to a dataframe without losing an
assigned dimname.

Here is an example that should illustrate what I'm talking about.

tableData <- state.x77[c(7, 38, 20, 46), c(7, 1, 8)]
names(dimnames(tableData)) <- c("State", "")
tableData

State? ? ? ? ? Frost Population? Area
? Connecticut? ? 139? ? ?  3100? 4862
? Pennsylvania?  126? ? ? 11860 44966
? Maryland? ? ?  101? ? ?  4122? 9891
? Virginia? ? ? ? 85? ? ?  4981 39780

tableData <- as.data.frame(tableData)
tableData

? ? ? ? ? ?  Frost Population? Area
Connecticut? ? 139? ? ?  3100? 4862
Pennsylvania?  126? ? ? 11860 44966
Maryland? ? ?  101? ? ?  4122? 9891
Virginia? ? ? ? 85? ? ?  4981 39780

Notice how "State" gets removed when converting to a dataframe. How
can I get a dataframe with a separate column called "State" instead of
having the state become the row.names? I can think of an ugly way to do it but
suspect there must be something more elegant.

Thanks,

Paul

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Paul Miller

2013-Apr-10 15:44 UTC

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[R] Converting matrix to data frame without losing an assigned dimname

Hi David, Gabor, Arun, and Rolf,
?
Thanks for your replies to my question. Very interesting and very helpful. I
particularly liked the one-line solutions proposed by David and Gabor.?I had a
suspicion that this conversion could be done using only a minimal amount of
code.
?
For what I'm doing,?it's helpful to have a "State" column that
is character. For that reason, David's solution might be the best in this
particular instance.
?
Thanks again everyone.
?
Paul
?

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