2014年4月9日 · Use subset.ffdf from package ffbase. Subset is a generic function in R, and ffbase implements it for ffdf objects. So you can just use subset as you would do with a regular data frame.

2012年9月18日 · Trying to learn about ffdf output, I entered command lines such as dim(B2010), str(B2010), ls(B2010), etc. dim(B2010) resulted in the appropriate number of rows but only one column (a string per record of the values separated by commas), and ls(B2010) outputted “[1] "physical" "row.names" "virtual" instead of the usual list of variables.

2014年3月3日 · The package ffbase provides many base functions for ff/ffdf objects, including subset.ff. With a bit of limited testing, it seems that subset.ff is relatively fast. Try loading ffbase and then using the simpler code you suggested from a …

I am trying to create an ffdf dataframe by merging and appending two existing ffdf dataframes. The ffdfs have different numbers of columns and different row numbers. I know that merge() performs only inner and left outer joins while ffdfappend() will not allow appending if columns are not identical. I am wondering if anyone has a workaround for ...

2014年8月19日 · This is basically asking how to apply a previous question to a ffdf : R - applying ifelse to a whole data frame. I am basically trying to do the same thing. Given a ffdf dataframe, I am basically asking how to apply an ifelse to the entire dataframe. See the two examples that work on test (a data frame). I'm trying to do the same to test.ffdf.

2015年7月23日 · I have a very large data set that I have to use as an ffdf, and am stuck trying to fill NA values using a last observation carried forward operation. Below is a sample of what the data looks like I'm

2014年3月3日 · I need an outer join of ffdf dataframes saved in a list. Have checked this, but it refers to a different problem. Example code for RAM objects: x1 = data.frame(name='a1', Ai=2, Ac=1, Bi=1) x2 = data.

2013年11月11日 · But I assume you have a ffdf with all columns of the same type, otherwise it does not make sense to convert it to an ff vector or ff matrix. If you want to convert to an ff matrix, you can use as.ff_matrix.ffdf which is unexported in ffbase, so access it with ffbase:::as.ff_matrix.ffdf as in the following example.

2014年2月19日 · An ffdf is basically a list with elements "virtual", "physical", "row.names". If you do an lapply over the physical element, you have what you want.

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