[R] simple question on data frames assignment

[Jeff Newmiller]

lapply(colordata2[ -1 ], f )

When you put the parentheses on, you are calling the function yourself before lapply gets a chance. The error pops up because you are giving a vector of numbers (the answer f gave you) to the second argument of lapply instead of a function. 
-- 
Sent from my phone. Please excuse my brevity.

On April 7, 2016 7:31:18 AM PDT, Michael Artz <michaeleartz at gmail.com> wrote:
>If you are not using an anonymous function and say you had written the
>function out
>
>The below gives me the error > 'f(colordata2$color1)' is not a
>function,
>character or symbol'  But then how is the anonymous function working?
>
>
>f <- function(col){
>  ifelse(col == 'blue', 1, 0)
>}
>responses <- lapply(colordata2[ -1 ], f(colordata2$color1) )
>
>'f(colordata2$color1)' is not a function, character or symbol'
>
>then how could you then use this fuction in lapply if not for the
>anonymous
>function?
>
>On Thu, Apr 7, 2016 at 8:17 AM, Jeff Newmiller
><jdnewmil at dcn.davis.ca.us>
>wrote:
>
>> Lapply is not a vectorized function. It is compact to read, but it
>would
>> not be worth using for this calculation.
>>
>> However, if your data frame had multiple color columns in your data
>frame
>> that you wanted to make responses for then you might want to use
>lapply as
>> a more compact version of a for loop to repeat this operation.
>>
>> colordata2 <- data.frame(id = c(1,2,3,4,5), color1 = c("blue", "red",
>> "green", "blue", "orange"), color2 = c("orange", "green",
>> "blue", "red", "red"))
>> responses <- lapply( colordata2[ -1 ], function(col) { ifelse(col ==
>> 'blue', 1, 0) } )
>> names(responses) <- names( colordata2 )[-1]
>>
>> where each of the columns other than the first is handed in turn to
>the
>> anonymous function that does the response calculation. The result is
>a data
>> frame (list of columns) with no column names, so I give the new
>columns
>> names based on the old column names. You could choose different
>names, e.g.
>>
>> names(responses) <- paste0( "response", 1:2 )
>>
>> but you have to be careful to fix that code whenever you change the
>> colordata2 data frame to have more columns.
>> --
>> Sent from my phone. Please excuse my brevity.
>>
>> On April 7, 2016 4:57:04 AM PDT, Michael Artz
><michaeleartz at gmail.com>
>> wrote:
>>>
>>> Thaks so much!  And how would you incorporate lapply() here?
>>>
>>> On Thu, Apr 7, 2016 at 6:52 AM, David Barron <dnbarron at gmail.com>
>wrote:
>>>
>>>  ifelse is vectorised, so just use that without the loop.
>>>>
>>>>  colordata$response <- ifelse(colordata$color == 'blue', 1, 0)
>>>>
>>>>  David
>>>>
>>>>  On 7 April 2016 at 12:41, Michael Artz <michaeleartz at gmail.com>
>wrote:
>>>>
>>>>  Hi I'm not sure how to ask this, but its a very easy question to
>answer
>>>>>  for
>>>>>  an R person.
>>>>>
>>>>>  What is an easy way to check for a column value and then assigne
>a new
>>>>>  column a value based on that old column value?
>>>>>
>>>>>  For example, Im doing
>>>>>   colordata <- data.frame(id = c(1,2,3,4,5),
>>>>> color = c("blue", "red",
>>>>>  "green", "blue", "orange"))
>>>>>   for (i in 1:nrow(colordata)){
>>>>>     colordata$response[i] <- ifelse(colordata[i,"color"] ==
>"blue", 1, 0)
>>>>>   }
>>>>>
>>>>>  which works,  but I don't want to use the for loop I want to
>"vecotrize"
>>>>>  this.  How would this be implemented?
>>>>>
>>>>>          [[alternative HTML version deleted]]
>>>>>
>>>>> ------------------------------
>>>>>
>>>>>  R-help at r-project.org mailing list -- To UNSUBSCRIBE and more, see
>>>>>  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.
>>>>
>>>>
>>>>
>>>
>>>  [[alternative HTML version deleted]]
>>>
>>> ------------------------------
>>>
>>> R-help at r-project.org mailing list -- To UNSUBSCRIBE and more, see
>>> 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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