grid.Rmd
Closed sorts (or Qsorts) are accomplished using 2dimensional grids, usually for ranking items across the (horizontal) xaxis, with the (vertical) yaxis used to stack ties.^{1}
pensieve records such grids as psGrid
s, simple 2dimensional matrices, where each cell is either TRUE
or FALSE
depending on whether the cell is allowed. It can be constructed by providing an arbitrary matrix.
library(pensieve)
m < matrix(data = c(FALSE, TRUE, TRUE, TRUE, FALSE, TRUE), nrow = 2)
grid < psGrid(grid = m)
grid
In Q methodology, these grids are often specified in a shorthand way, by giving a vector of column heights (number of allowed ties) from the left to the right. This vector of heights — somewhat akin to a histogram — is sometimes also known as a Q distribution. pensieve offers a convenient method to coerce such vectors into psGrid
s.
The shorthand vector notation implies that there are never any disallowed cells at the bottom of the grid, or anywhere in the middle of other allowed cells. This makes sense when using rectangular grids with the allowed ties approximating a normal distribution, as is often the case.
There is however no reason to assume that all sorts follow such strictures, and the logical psGrid
is a more flexible generalisation.
A psGrid
implies two pieces of information about a sorting study:
psItems
), it specifies whether a distribution is forced or free. Under a forced distribution, there will be exactly as many allowed cells (TRUE
, 19 in the above example) as there are items, forcing participants to occupy every cell. Under a free distribution, there will be more cells than items, and participants will be flexible in which of the allowed cells they actually use.Distributions are sometimes only reported for forced distributions, but it should be noted that all closed sorts use a grid. Even under a completely free distribution (with all cells TRUE
), there is a maximum number of ranks and ties, if simply implied by the size of the table used.
Most pensieve functions do not require a psGrid
, but the design choices it stores can be helpful for validating data and enhance analysis and output methods. Specifying a psGrid
is highly recommended.
For optional arguments, see psGrid()
.
pensieve offers a knit_print()
method to visualise psGrid
s from inside knitr chunks. You can type knit_print(grid)
, or simply grid
as in the above chunks. Currently only output from chunks (not inline) and to HTMLoutputs (not PDF, Word or others) is supported.
pensieve also offers experimental support for (loosely defined) hexagonally tiled grids, though these have limited support in other parts of the package. For details, see psGrid()
.
offset = NULL 
offset = 'even' 
offset = 'odd' 


polygon = 'rectangle' 
Chessboard (default)  Brick wall  Brick wall 
polygon = 'hexagon' 
–  Honeycomb  Honeycomb 
In this sense, strictly speaking, the ydimension of the grid is often meaningless.↩