# Unstack one Set of Variables from Long to Wide `unstack2` converts one set of variables in a data.frame from long to wide format. (If you want to convert multiple sets of variables from long to wide, see `reshape`.) It is a modified version of `unstack` that 1) requires a column for the rownames of the data.frame (or equivalently an id column with unique values for each row in the wide format) before it was stacked, 2) can retain additional columns not being unstacked, and 3) can order by rownames original positions rather than their alphanumerical order. ```r unstack2( data, rownames.nm = "row_names", vrbnames.nm = "vrb_names", el.nm = "el", keep.nm = pick(x = names(data), val = c(rownames.nm, vrbnames.nm, el.nm), not = TRUE), add.missing = TRUE, rownamesAsColumn = FALSE ) ``` ## Arguments - `data`: data.frame of data containing stacked variables. - `rownames.nm`: character vector of length 1 specifying the colname in `data` for whom its unique values correspond to the rows in the return object. - `vrbnames.nm`: character vector of length 1 specifying the colname in ```data``` that contains the names of the variables to be unstacked. - `el.nm`: character vector of length 1 specifying the colname in `data` containing the elements from the variable to be unstacked. - `keep.nm`: optional argument containing a character vector of colnames from `data` specifying the additional columns to be included in the return object. The default is all the other columns in the data.frame besides `rownames.nm`, `vrbnames.nm`, and `el.nm`. If NULL, then no additional columns are retained. The `keep.nm` columns will be the last (aka most right) columns in the return object. - `add.missing`: logical vector of length 1 specifying whether missing values should be added when unstacking. This will occur if there are unequal number of rows for each variable in the set. If FALSE, an error will be returned when there are an unequal number of rows and missing values would need to be added to create the returned data.frame. - `rownamesAsColumn`: logical vector of length 1 specifying whether the unique values in `rownames.nm` column should be a column in the return object (TRUE) or the rownames of the return object (FALSE). ## Returns data.frame with nrow = `length(unique(data[[rownames.nm]]))` from unstacking the elements of `el.nm` alongside one another. New columns are created for each unique value in `vrbnames.nm` as well as columns for any colnames additional specified by `keep.nm`. If `rownamesAsColumn` = TRUE, then the first column is the unique values in `rownames.nm`; otherwise, they are the rownames of the return object (default). ## Details `unstack2` is also very similar to `reshape::cast.data.frame`. The differences are that it 1) can return the rownames as rownames of the returned data.frame rather than an id column, 2) can retain additional columns not being unstacked, and 3) can order by rownames original positions rather than the variable names being stacked call order. ## Examples ```r # ordered by rownames stacked <- stack2(data = mtcars, select.nm = c("disp","hp","drat","wt","qsec"), keep.nm = c("vs","am"), order.by.rownames = TRUE) x <- unstack2(stacked) # ordered by vrbnames stacked <- stack2(data = mtcars, select.nm = c("disp","hp","drat","wt","qsec"), keep.nm = c("vs","am"), order.by.rownames = FALSE) y <- unstack2(stacked) identical(x, y) # rownames as a column z <- unstack2(data = stacked, rownamesAsColumn = TRUE) # compare to utils:::unstack.data.frame and reshape::cast stacked <- stack2(data = mtcars, select.nm = c("disp","hp","drat","wt","qsec"), keep.nm = c("vs","am")) x <- unstack(x = stacked, form = el ~ vrb_names) # automatically sorts the colnames alphabetically y <- reshape::cast(data = stacked, formula = row_names ~ vrb_names, value = "el") # automatically sorts the rownames alphabetically z <- unstack2(stacked) # is able to keep additional variables head(x); head(y); head(z) # unequal number of rows for each unique value in `data`[[`vrbnames.nm`]] # this can occur if you are using unstack2 without having called stack2 right before row_keep <- sample(1:nrow(stacked), size = nrow(stacked) / 2) stacked_rm <- stacked[row_keep, ] unstack2(data = stacked_rm, rownames.nm = "row_names", vrbnames.nm = "vrb_names", el.nm = "el") ## Not run: # error when `add.missing` = FALSE unstack2(data = stacked_rm, rownames.nm = "row_names", vrbnames.nm = "vrb_names", el.nm = "el", add.missing = FALSE) ## End(Not run) ``` ## See Also `stack2` `unstack` `cast`

unstack2 function