R help - Aug 2019 - Use gather with a various number of columns

Hello,
I'm using the gather function from the tidyr package to reshape data.frames.
For example, for the the following dataframe, I apply the command
below.df_initial<-data.frame(col1name=c(1,2,3,4,5,6,7),
col2name=c(4,5,6,7,8,9,1),
col3name=c(9,8,7,6,5,4,3))df_reshaped<-gather(df_initial,
"col1name", "col2name", "col3name",
key="colall", value="value")

In this example, there are 3 columns because there were 3 devices. But the
number of devices can change and I would like to avoid adding new columns by
hand in the 'gather' command.
Is there a way to adapt the command so that it automatically detect the number
of columns of df_initial :

df_initial<-data.frame(col1name=c(1,2,3,4,5,6,7), col2name=c(4,5,6,7,8,9,1),
col3name=c(9,8,7,6,5,4,3))
df_initial<-data.frame(col1name=c(1,2,3,4,5,6,7), col2name=c(4,5,6,7,8,9,1))
df_initial<-data.frame(col1name=c(1,2,3,4,5,6,7), col2name=c(4,5,6,7,8,9,1),
col3name=c(9,8,7,6,5,4,3), col4name=c(5,6,8,9,7,4,1))
df_reshaped_auto<-gather(df_initial, ?????????, key="colall",
value="value")

Thanks in advance to help me replace??????????,Ptit Bleu.

	[[alternative HTML version deleted]]

Hello,

Just don't include the names of those columns.
Is this what you want?


library(tidyr)

df_initial1 <- data.frame(col1name=c(1,2,3,4,5,6,7),  
col2name=c(4,5,6,7,8,9,1), col3name=c(9,8,7,6,5,4,3))
df_initial2 <- data.frame(col1name=c(1,2,3,4,5,6,7),  
col2name=c(4,5,6,7,8,9,1))
df_initial3 <- data.frame(col1name=c(1,2,3,4,5,6,7),  
col2name=c(4,5,6,7,8,9,1), col3name=c(9,8,7,6,5,4,3),  
col4name=c(5,6,8,9,7,4,1))

gather(df_initial1, key="colall", value="value")
gather(df_initial2, key="colall", value="value")
gather(df_initial3, key="colall", value="value")


Hope this helps,

Rui Barradas









Citando lionel sicot via R-help <r-help at r-project.org>:
> Hello,
> I'm using the gather function from the tidyr package to reshape
data.frames.
> For example, for the the following dataframe, I apply the command  
> below.df_initial<-data.frame(col1name=c(1,2,3,4,5,6,7),  
> col2name=c(4,5,6,7,8,9,1),  
> col3name=c(9,8,7,6,5,4,3))df_reshaped<-gather(df_initial,  
> "col1name", "col2name", "col3name",
key="colall", value="value")
>
> In this example, there are 3 columns because there were 3 devices.  
> But the number of devices can change and I would like to avoid  
> adding new columns by hand in the 'gather' command.
> Is there a way to adapt the command so that it automatically detect  
> the number of columns of df_initial :
>
> df_initial<-data.frame(col1name=c(1,2,3,4,5,6,7),  
> col2name=c(4,5,6,7,8,9,1), col3name=c(9,8,7,6,5,4,3))
> df_initial<-data.frame(col1name=c(1,2,3,4,5,6,7),
col2name=c(4,5,6,7,8,9,1))
> df_initial<-data.frame(col1name=c(1,2,3,4,5,6,7),  
> col2name=c(4,5,6,7,8,9,1), col3name=c(9,8,7,6,5,4,3),  
> col4name=c(5,6,8,9,7,4,1))
> df_reshaped_auto<-gather(df_initial, ?????????, key="colall",
value="value")
>
> Thanks in advance to help me replace??????????,Ptit Bleu.
>
> 	[[alternative HTML version deleted]]
>
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