assign values to empty row in R
I have a function that returns a data frame with more than 50 columns (one row).
This function is called inside a loop (lapply) so I get a list of dataframes one row each.
I initialize an empty dataframe at the very beginning in the function to be populated with the actual data returned by the process (short version here for testing)
df <- read.csv(text = "conn,pc,server,profile")
R> df
[1] conn pc server profile car id amount
<0 rows> (or 0-length row.names)
I would like to assign values to the row taking into account that the process sometimes does not return values for all columns.
Similar SO questions tend to rely on initializing data frame this way:
df <- data.frame("conn"= NA, "pc"= NA, "server"= NA, "profile" = NA)
but I don't want a row of NAs in case there's no value returned.
So in my function I tried first:
returned.conn.value <- 3 # assigned by hand for the sake of simplicity
df$conn <- returned.conn.value
Error in `$<-.data.frame`(`*tmp*`, conn, value = 3) :
replacement has 1 row, data has 0
So I discovered there's no way of adding value to a column inside an empty dataframe, but.....
df[1,1] <- 3
This, to my surprise, worked. But, I consider very ugly to assign values to columns by index, so I tried this:
grep("^conn$", colnames(df))
[1] 1
Uglier indeed, as it's forcing me to write the very same line for every column (instead of counting by hand, yes)
So, I'm afraid I took a dead road leading to nowhere.
is there any way of initialize an empty dataframe as it will allow me to do simple assignments as the one below with no issue?
df$conn <- 3
Any hint will be much appreciated.
r dataframe
asked Nov 14 '18 at 16:16
ForgeForge
374316
add a comment |
I have a function that returns a data frame with more than 50 columns (one row).
This function is called inside a loop (lapply) so I get a list of dataframes one row each.
I initialize an empty dataframe at the very beginning in the function to be populated with the actual data returned by the process (short version here for testing)
df <- read.csv(text = "conn,pc,server,profile")
R> df
[1] conn pc server profile car id amount
<0 rows> (or 0-length row.names)
I would like to assign values to the row taking into account that the process sometimes does not return values for all columns.
Similar SO questions tend to rely on initializing data frame this way:
df <- data.frame("conn"= NA, "pc"= NA, "server"= NA, "profile" = NA)
but I don't want a row of NAs in case there's no value returned.
So in my function I tried first:
returned.conn.value <- 3 # assigned by hand for the sake of simplicity
df$conn <- returned.conn.value
Error in `$<-.data.frame`(`*tmp*`, conn, value = 3) :
replacement has 1 row, data has 0
So I discovered there's no way of adding value to a column inside an empty dataframe, but.....
df[1,1] <- 3
This, to my surprise, worked. But, I consider very ugly to assign values to columns by index, so I tried this:
grep("^conn$", colnames(df))
[1] 1
Uglier indeed, as it's forcing me to write the very same line for every column (instead of counting by hand, yes)
So, I'm afraid I took a dead road leading to nowhere.
is there any way of initialize an empty dataframe as it will allow me to do simple assignments as the one below with no issue?
df$conn <- 3
Any hint will be much appreciated.
r dataframe
asked Nov 14 '18 at 16:16
ForgeForge
374316
I don't know how to do this inside of an empty data.frame, but you could do it inside separate vectors and cbind them at the end?
– Adam K
Nov 14 '18 at 17:35
Not really. The data flow only allows me to get a data frame every time the function is called. I can’t imagine how to gather results into vectors and then cbind....
– Forge
Nov 14 '18 at 18:24
add a comment |
I have a function that returns a data frame with more than 50 columns (one row).
This function is called inside a loop (lapply) so I get a list of dataframes one row each.
I initialize an empty dataframe at the very beginning in the function to be populated with the actual data returned by the process (short version here for testing)
df <- read.csv(text = "conn,pc,server,profile")
R> df
[1] conn pc server profile car id amount
<0 rows> (or 0-length row.names)
I would like to assign values to the row taking into account that the process sometimes does not return values for all columns.
Similar SO questions tend to rely on initializing data frame this way:
df <- data.frame("conn"= NA, "pc"= NA, "server"= NA, "profile" = NA)
but I don't want a row of NAs in case there's no value returned.
So in my function I tried first:
returned.conn.value <- 3 # assigned by hand for the sake of simplicity
df$conn <- returned.conn.value
Error in `$<-.data.frame`(`*tmp*`, conn, value = 3) :
replacement has 1 row, data has 0
So I discovered there's no way of adding value to a column inside an empty dataframe, but.....
df[1,1] <- 3
This, to my surprise, worked. But, I consider very ugly to assign values to columns by index, so I tried this:
grep("^conn$", colnames(df))
[1] 1
Uglier indeed, as it's forcing me to write the very same line for every column (instead of counting by hand, yes)
So, I'm afraid I took a dead road leading to nowhere.
is there any way of initialize an empty dataframe as it will allow me to do simple assignments as the one below with no issue?
df$conn <- 3
Any hint will be much appreciated.
r dataframe
asked Nov 14 '18 at 16:16
ForgeForge
374316
I have a function that returns a data frame with more than 50 columns (one row).
This function is called inside a loop (lapply) so I get a list of dataframes one row each.
I initialize an empty dataframe at the very beginning in the function to be populated with the actual data returned by the process (short version here for testing)
df <- read.csv(text = "conn,pc,server,profile")
R> df
[1] conn pc server profile car id amount
<0 rows> (or 0-length row.names)
I would like to assign values to the row taking into account that the process sometimes does not return values for all columns.
Similar SO questions tend to rely on initializing data frame this way:
df <- data.frame("conn"= NA, "pc"= NA, "server"= NA, "profile" = NA)
but I don't want a row of NAs in case there's no value returned.
So in my function I tried first:
returned.conn.value <- 3 # assigned by hand for the sake of simplicity
df$conn <- returned.conn.value
Error in `$<-.data.frame`(`*tmp*`, conn, value = 3) :
replacement has 1 row, data has 0
So I discovered there's no way of adding value to a column inside an empty dataframe, but.....
df[1,1] <- 3
This, to my surprise, worked. But, I consider very ugly to assign values to columns by index, so I tried this:
grep("^conn$", colnames(df))
[1] 1
Uglier indeed, as it's forcing me to write the very same line for every column (instead of counting by hand, yes)
So, I'm afraid I took a dead road leading to nowhere.
is there any way of initialize an empty dataframe as it will allow me to do simple assignments as the one below with no issue?
df$conn <- 3
Any hint will be much appreciated.
r dataframe
r dataframe
asked Nov 14 '18 at 16:16
ForgeForge
374316
asked Nov 14 '18 at 16:16
ForgeForge
374316
asked Nov 14 '18 at 16:16
ForgeForge
374316
asked Nov 14 '18 at 16:16
ForgeForge
374316
asked Nov 14 '18 at 16:16
ForgeForge
374316
374316
I don't know how to do this inside of an empty data.frame, but you could do it inside separate vectors and cbind them at the end?
– Adam K
Nov 14 '18 at 17:35
Not really. The data flow only allows me to get a data frame every time the function is called. I can’t imagine how to gather results into vectors and then cbind....
– Forge
Nov 14 '18 at 18:24
add a comment |
I don't know how to do this inside of an empty data.frame, but you could do it inside separate vectors and cbind them at the end?
– Adam K
Nov 14 '18 at 17:35
Not really. The data flow only allows me to get a data frame every time the function is called. I can’t imagine how to gather results into vectors and then cbind....
– Forge
Nov 14 '18 at 18:24
I don't know how to do this inside of an empty data.frame, but you could do it inside separate vectors and cbind them at the end?
– Adam K
Nov 14 '18 at 17:35
I don't know how to do this inside of an empty data.frame, but you could do it inside separate vectors and cbind them at the end?
– Adam K
Nov 14 '18 at 17:35
Not really. The data flow only allows me to get a data frame every time the function is called. I can’t imagine how to gather results into vectors and then cbind....
– Forge
Nov 14 '18 at 18:24
Not really. The data flow only allows me to get a data frame every time the function is called. I can’t imagine how to gather results into vectors and then cbind....
– Forge
Nov 14 '18 at 18:24
add a comment |
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I don't know how to do this inside of an empty data.frame, but you could do it inside separate vectors and cbind them at the end?
– Adam K
Nov 14 '18 at 17:35
Not really. The data flow only allows me to get a data frame every time the function is called. I can’t imagine how to gather results into vectors and then cbind....
– Forge
Nov 14 '18 at 18:24