R-language throws error (list) object cannot be coerced to type ‘double‘ when we try to convert a list of string or other type values to a numeric vector.
To correctly coerce a list, you should unlist it first and then convert into numeric vector.
a <- structure(list(`X$Days` = c("10", "38", "66", "101", "129", "185", "283","374")), .Names = "X$Days")
as.numeric(unlist(a))
There are different types of objects in R which could be coerced during computations. Some of these objects are –
"NULL" |
NULL |
"symbol" |
a variable name |
"pairlist" |
a pairlist object (mainly internal) |
"closure" |
a function |
"environment" |
an environment |
"promise" |
an object used to implement lazy evaluation |
"language" |
an R language construct |
"special" |
an internal function that does not evaluate its arguments |
"builtin" |
an internal function that evaluates its arguments |
"char" |
a ‘scalar’ string object (internal only) *** |
"logical" |
a vector containing logical values |
"integer" |
a vector containing integer values |
"double" |
a vector containing real values |
"complex" |
a vector containing complex values |
"character" |
a vector containing character values |
"..." |
the special variable length argument *** |
"any" |
a special type that matches all types: there are no objects of this type |
"expression" |
an expression object |
"list" |
a list |
"bytecode" |
byte code (internal only) *** |
"externalptr" |
an external pointer object |
"weakref" |
a weak reference object |
"raw" |
a vector containing bytes |
"S4" |
an S4 object which is not a simple object |
Some other examples of coercion are –
> labs <- paste(c("X","Y"), 1:10, sep="")
c("X1", "Y2", "X3", "Y4", "X5", "Y6", "X7", "Y8", "X9", "Y10")
Here we used paste() function which takes an arbitrary number of arguments and concatenates them one by one into character strings. So, they are coerced into characters.
According to R manuals –
A list whose components conform to the restrictions of a data frame may be coerced into a data frame using the function
as.data.frame()
Live Demo
