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APPENDIX B:  THE IDL LIBRARYy763qc(0,14848)\1f1 7f0 6f1 2f0 6f1
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IDL REFERENCE MANUALy763qc\5f1 9f0 1f1
Appendix Be18c(635)\f6b9f0 1f6
The IDL Librarye12c\b
Although the user of IDL is encouraged to use the flexibility of the system to construct his own analysis tools, the IDL system provides a library which contains some useful combinations of IDL operators as functions.  Often the real benefit of these functions is simply that they provide more detailed labelling than the user immersed in a specific problem would be willing to provide or that they make use of operator combinations which, although simple, would require some amount of thought to derive.e12j\f6 21f1 3f6 93f1 3f6 70f1 3f6
As they are expressed as IDL programs, the user is encouraged to study the text of these definitions as indication of how the IDL primitives may be combined together to produce new functionality.  The descriptions here are correspondingly brief.e12j\f6 25f1 3f6 98f1 3f6
The Library may be LOADed from <IDL>LIBRARY (source code for perusal) and <IDL>LIBRARY.COM (compiled code for unreflective execution).  This listing is for convenience only, and the contents of the Library are subject to change without notice.e12j\f6 19f1 4f0 2f6 6f1 13f0 25f6 5f1 17f0 42f6
apool[atable;lines]e18\5f6
Pools the specified lines of the ANOVA table atable, producing a vector of the SS, df, and MS.l4233j\20b5B8f1 5f0 7b6B28f1 2f0 10f1 2f0 1f6
freq[a;wt]e12\4f6
Computes frequency distribution of the values in an arbitrary array a, weighted by wt.  Not extended, because there might be different numbers of values for different slices.l4233j\68b1B14b2B89f6
freqhist[a;file;wt]e12\8f6
Produces frequency histograms of the values of a, weighted by wt, for each level of its kept dimensions.  Returns file.l4233j\47b1B14b2B50f6b4f0B1f6
friedman[m]e12\8f6
Computes the Friedman 2-way analysis-of-variance by ranks. Columns are the repeated measure.  The sign test is essentially the special case where there are only two columns.  Produces the Chi-square/r statistic, which may be looked up in Segal, or referred to the chi-square distribution with C-1 degrees of freedom, for C the number of columns.l4233j\293f1 1f0 27f1 1f0 23f6
hmean[a]e12\5f6
Computes the harmonic mean of the non-NIL elements of a.l4233j\38f1 3f0 13b1B1f6
kruskal-wallis[values;attribs]e12\14f6
Computes the Kruskal-Wallis analysis-of-variance by ranks. Produces the H statistic, which may be looked up in Segal, or referred to the chi-square distribution with K-1 degrees of freedom, for K the number of groups. values can be a grouped array, with the treatment dimension the only kept dimension, or it can be a vector of values, with the classification indicated by attribs.l4233j\72f1 1f0 93f1 1f0 27f1 1f0 23b6B149b7B1f6
mann-whitney[values;attribs]e12\12f6
Essentially the special case of the Kruskal-Wallis analysis-of-variance by ranks where there are only two groups.l4233j\113f6
nfroms[m]e12\6f6
Returns the N on which a swept cross-product matrix m is based, no matter what the pattern of sweeping has been, by sweeping in all the variables that are swept out.  Doesn't work if anything has been swept out or in twice.l4233j\12f1 1f0 39b1B170f6
pct[a;keeps]e12\3f6
Returns an image of a with elements indicating the percentage that the corresponding element a is of the margin formed by collapsing across all dimensions not in keeps.  For example, for a matrix, keeps=1 gives row percentages; keeps=2 gives column percentages.l4233j\20b1B72b1B68b5B30b5B26b5B28f6
regress[pre;post;dv;n]e12\7f6
Produces a more-or-less standard regression table for the dependent variables in the selector dv, given a pre-swept matrix pre and a post-swept matrix post.  If dv=NIL, then tables for all unswept variables in post are constructed.  If n is not NIL, then it is the total number of observations on which the regression should be based.  Otherwise, the n is computed using NFROMS.  The user should provide the n if the constant is not present in the array, e.g., because it was NORMed.l4233j\94b2B27b3B7b4B14b4B6b2B1f1 3f0 43b4B22b1B8f1 3f0 103b1B19f1 6f0 31b1B67f1 4f0 3f6
rmse[x;y]e12\4f6
Computes the root-mean-square-error of the conformable arrays x and y.l4233j\62b1B5b1B1f6
signtest[v1;v2]e12\8f6
Produces a frequency table to which chi-square can be applied for the sign-test.l4233j\80f6
wilcoxen[v1;v2]e12\8f6
Produces the Wilcoxon statistic to be looked up in tables (for N<25), or computes the correct probability using ANOVA.l4233j\63f1 1f0 48f1 5f0 1f6
yhat[m;sw;dv]e12\4f6
Computes predicted values for variables in m, given the swept matrix sw and the dependent variable selector dv.  If dv is NIL, then predictors for all unswept variables in sw are computed.l4233j\43b1B25b2B37b2B6b2B4f1 3f0 47b2B14f6
zscore[a;mom]e12\6f6
Computes the image of a under the zscore mapping.  mom, if given, is the MOMENTS table for a.  Otherwise, zscore will compute them for itself.l4233j\22b1B28b3B19f1 7f0 11b1B50f6