[R] Converting a list to a data frame

[Duncan Murdoch]

On 24/07/2021 5:40 p.m., Rui Barradas wrote:
> Hello,
> 
> No, it's not possible to work with a matrix in ggplot2.
> Not even with an object of class "list".

If that's the main thing Jeff is doing, then he should convert to a 
dataframe.  But it *is* possible to work with the original matrix in 
ggplot2, just not very natural:
> 
> 
> 
> l <- list(x=1:5, y=1:5)
> d <- as.data.frame(l)
> m <- as.matrix(d)
> 
> library(ggplot2)
> ggplot(l, aes(x, y)) + geom_point()  # Error
> ggplot(d, aes(x, y)) + geom_point()  # OK, as expected
> ggplot(m, aes(x, y)) + geom_point()  # Error

ggplot(NULL, aes(x=m[,"x"], y=m[,"y"])) + geom_point() # OK

Duncan Murdoch

> 
> 
> 
> Hope this helps,
> 
> Rui Barradas
> 
> 
> Às 22:31 de 24/07/21, Jeff Reichman escreveu:
>> Duncan
>>
>> I need to plot the results (ggplot2) and I'm thinking I can only use a data.frame object in ggplot2. It is a rath r large "list" over 1 million rows. It is possible to work with a matrix in ggplot2?
>>
>> Jeff
>>
>> -----Original Message-----
>> From: Duncan Murdoch <murdoch.duncan using gmail.com>
>> Sent: Saturday, July 24, 2021 12:03 PM
>> To: reichmanj using sbcglobal.net; R-help using r-project.org
>> Subject: Re: [R] Converting a list to a data frame
>>
>> Others have shown you how to extract the matrix and convert it to a dataframe.  My only addition is to suggest that you don't do this:
>> matrix methods are often much more efficient than dataframe methods, so if you can work with the matrix without conversion, you'll often find things run a lot faster.
>>
>> Duncan Murdoch
>>
>> On 24/07/2021 9:18 a.m., Jeff Reichman wrote:
>>> How does one convert a list into a data frame?
>>>
>>>     
>>>
>>>> str(weight_chains)
>>>
>>> List of 1
>>>
>>> $ : 'mcmc' num [1:100000, 1:3] -105 -105 -105 -104 -103 ...
>>>
>>>      ..- attr(*, "dimnames")=List of 2
>>>
>>>      .. ..$ : NULL
>>>
>>>      .. ..$ : chr [1:3] "a" "b" "s"
>>>
>>>      ..- attr(*, "mcpar")= num [1:3] 1001 101000 1
>>>
>>> - attr(*, "class")= chr "mcmc.list"
>>>
>>>     
>>>
>>> Such that ..
>>>
>>>     
>>>
>>>>
>>>
>>> weight_chains
>>>
>>>
>>>
>>>                   a         b         s
>>>
>>> 1     -104.72512 1.0141407  9.369227
>>>
>>> 2     -104.52297 1.0167432  9.131354
>>>
>>> 3     -104.72669 1.0139528  9.219877
>>>
>>>     
>>>
>>>
>>> 	[[alternative HTML version deleted]]
>>>
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