NAG CL Interface
g11bcc (tabulate_​margin)

Settings help

CL Name Style:

1 Purpose

g11bcc computes a marginal table from a table computed by g11bac or g11bbc using a selected statistic.

2 Specification

#include <nag.h>
void  g11bcc (Nag_TableStats stat, const double table[], Integer ncells, Integer ndim, const Integer idim[], const Integer isdim[], double sub_table[], Integer maxst, Integer *mcells, Integer *mdim, Integer mlevel[], double comm_ar[], NagError *fail)
The function may be called by the names: g11bcc, nag_contab_tabulate_margin or nag_tabulate_margin.

3 Description

For a dataset containing classification variables (known as factors) the functions g11bac and g11bbc compute a table using selected statistics, for example the mean or the median. The table is indexed by the levels of the selected factors, for example if there were three factors A, B and C with 3, 2 and 4 levels respectively and the mean was to be tabulated the resulting table would be 3×2×4 with each cell being the mean of all observations with the appropriate combination of levels of the three factors. In further analysis the table of means averaged over C for A and B may be required; this can be computed from the full table by taking the mean over the third dimension of the table, C.
In general, given a table computed by g11bac or g11bbc, g11bcc computes a sub-table defined by a subset of the factors used to define the table such that each cell of the sub-table is the selected statistic computed over the remaining factors. The statistics that can be used are the total, the mean, the median, the variance, the smallest and the largest value.

4 References

John J A and Quenouille M H (1977) Experiments: Design and Analysis Griffin
Kendall M G and Stuart A (1969) The Advanced Theory of Statistics (Volume 1) (3rd Edition) Griffin
West D H D (1979) Updating mean and variance estimates: An improved method Comm. ACM 22 532–555

5 Arguments

1: stat Nag_TableStats Input
On entry: indicates which statistic is to be used to compute the marginal table.
The total.
The average or mean.
The median.
The variance.
The largest value.
The smallest value.
Constraint: stat=Nag_TableStatsNObs, Nag_TableStatsAv, Nag_TableStatsMedian, Nag_TableStatsVar, Nag_TableStatsLarge or Nag_TableStatsSmall.
2: table[ncells] const double Input
On entry: the table as computed by g11bac or g11bbc.
3: ncells Integer Input
On entry: the number of cells in table as returned by g11bac or g11bbc.
4: ndim Integer Input
On entry: the number of dimensions for table as returned by g11bac or g11bbc.
Constraint: ndim2.
5: idim[ndim] const Integer Input
On entry: the number of levels for each dimension of table as returned by g11bac or g11bbc.
Constraint: idim[i]2, for i=0,1,,ndim-1.
6: isdim[ndim] const Integer Input
On entry: indicates which dimensions of table are to be included in the sub-table. If isdim[i-1]>0 the dimension or factor indicated by idim[i-1] is to be included in the sub-table, otherwise it is excluded.
7: sub_table[maxst] double Output
On exit: the first mcells elements contain the sub-table computed using the statistic indicated by stat. The table is stored in a similar way to table with the mcells cells stored so that for any two dimensions the index relating to the dimension given later in idim changes faster. For further details see Section 9.
8: maxst Integer Input
On entry: the maximum size of sub-table to be computed.
Constraint: maxst the product of the levels of the dimensions of table included in the sub-table, sub_table.
9: mcells Integer * Output
On exit: the number of cells in the sub-table in sub_table.
10: mdim Integer * Output
On exit: the number of dimensions to the sub-table in sub_table.
11: mlevel[ndim] Integer Output
On exit: the first mdim elements contain the number of levels for the dimensions of the sub-table in sub_table. The remaining elements are not referenced.
12: comm_ar[dim] double Output
Note: the dimension, dim, of the array comm_ar must be at least
  • maxst when stat=Nag_TableStatsVar;
  • 1 otherwise.
On exit: if stat=Nag_TableStatsVar comm_ar contains the sub-table of means corresponding to the sub-table of variances in sub_table. Otherwise comm_ar is not referenced.
13: fail NagError * Input/Output
The NAG error argument (see Section 7 in the Introduction to the NAG Library CL Interface).

6 Error Indicators and Warnings

Dynamic memory allocation failed.
See Section 3.1.2 in the Introduction to the NAG Library CL Interface for further information.
On entry, argument value had an illegal value.
On entry, i=value and idim[i-1]=value.
Constraint: idim2.
On entry, ndim=value.
Constraint: ndim2.
On entry, maxst=value and minimum value for maxst=value.
Constraint: maxstproduct of the levels of the dimensions of the table included in the sub-table, sub_table.
On entry, ncells is incompatible with idim.
On entry, all elements of isdim>0.
On entry, no elements of isdim>0.
An internal error has occurred in this function. Check the function call and any array sizes. If the call is correct then please contact NAG for assistance.
See Section 7.5 in the Introduction to the NAG Library CL Interface for further information.
Your licence key may have expired or may not have been installed correctly.
See Section 8 in the Introduction to the NAG Library CL Interface for further information.

7 Accuracy

Only applicable when stat=Nag_TableStatsVar. In this case a one pass algorithm is used as describe in West (1979).

8 Parallelism and Performance

Background information to multithreading can be found in the Multithreading documentation.
g11bcc is threaded by NAG for parallel execution in multithreaded implementations of the NAG Library.
Please consult the X06 Chapter Introduction for information on how to control and interrogate the OpenMP environment used within this function. Please also consult the Users' Note for your implementation for any additional implementation-specific information.

9 Further Comments

The sub-tables created by g11bcc and stored in sub_table and, depending on stat, also in comm_ar are stored in the following way. Let there be m dimensions defining the table with dimension k having lk levels, then the cell defined by the levels i1,i2,,im of the factors is stored in sth cell given by
cj=k=j+ 1m lk   for ​ j= 1, 2,, n- 1   and   cm=1.  

10 Example

The data, given by John and Quenouille (1977), is for 3 blocks of a 3×6 factorial experiment. The data can be considered as a 3×6×3 table (i.e., blocks × treatment with 6 levels × treatment with 3 levels). This table is input and the 6×3 table of treatment means for over blocks is computed and printed.

10.1 Program Text

Program Text (g11bcce.c)

10.2 Program Data

Program Data (g11bcce.d)

10.3 Program Results

Program Results (g11bcce.r)