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Calling Functions in the R Language

Using R to Analyze Data in SAS/IML Matrices

The program in this section consists of four parts:

  1. Read the data into SAS/IML vectors.

  2. Transfer the data to R.

  3. Call R functions to analyze the data.

  4. Transfer the results of the analysis into SAS/IML vectors.

Read the data. The following statements read the Weight and Height variables from the Sashelp.Class data set into SAS/IML vectors with the same names:

proc iml;
use Sashelp.Class;
read all var {Weight Height};
close Sashelp.Class;
  • Transfer the data to R. The following statements run the ExportMatrixToR subroutine in order to transfer data from a SAS/IML matrix into an R matrix. The names of the corresponding R vectors that contain the data are w and h.

    /* send matrices to R */
    run ExportMatrixToR(Weight, "w");
    run ExportMatrixToR(Height, "h");
  • Call R functions to perform some analysis. The SUBMIT statement with the R option is used to send statements to R. Comments in R begin with a hash mark (#, also called a number sign or a pound sign).

    submit / R;
       Model    <- lm(w ~ h, na.action="na.exclude")         # a
       ParamEst <- coef(Model)                               # b
       Pred     <- fitted(Model)
       Resid    <- residuals(Model)

    The R program consists of the following steps:

    1. The lm function computes a linear model of w as a function of h. The na.action= option specifies how the model handles missing values (which in R are represented by NA). In particular, the na.exclude option specifies that the lm function should not omit observations with missing values from residual and predicted values. This option makes it easier to merge the R results with the original data when the data contain missing values.

    2. Various information is retrieved from the linear model and placed into R vectors named ParamEst, Pred, and Resid.

  • Transfer the data from R. The ImportMatrixFromR subroutine transfers the ParamEst vector from R into a SAS/IML vector named pe. This vector is printed by the SAS/IML PRINT statement. The predicted values (Pred) and residual values (Resid) can be transferred similarly. The parameter estimates are used to compute the predicted values for a series of hypothetical heights, as shown in Figure 11.3.

    run ImportMatrixFromR(pe, "ParamEst");
    print pe[r={"Intercept" "Height"}];
    ht = T( do(55, 70, 5) );
    A = j(nrow(ht),1,1) || ht;
    pred_wt = A * pe;
    print ht pred_wt;
  • Figure 11.3 Results from an R Analysis
    Intercept -143.0269
    Height 3.8990303

    ht pred_wt
    55 71.419746
    60 90.914898
    65 110.41005
    70 129.9052

    You cannot directly transfer the contents of the Model object. Instead, various R functions are used to extract portions of the Model object, and those simpler pieces are transferred.

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