[R] Implement feature info for DMatrix. (#8048)

R-package/R/xgb.DMatrix.R

@@ -54,7 +54,10 @@ xgb.DMatrix <- function(data, info = list(), missing = NA, silent = FALSE, nthre
     stop("xgb.DMatrix does not support construction from ", typeof(data))
   }
   dmat <- handle
-  attributes(dmat) <- list(.Dimnames = list(NULL, cnames), class = "xgb.DMatrix")
+  attributes(dmat) <- list(class = "xgb.DMatrix")
+  if (!is.null(cnames)) {
+    setinfo(dmat, "feature_name", cnames)
+  }
 
   info <- append(info, list(...))
   for (i in seq_along(info)) {
@@ -144,7 +147,9 @@ dim.xgb.DMatrix <- function(x) {
 #' @rdname dimnames.xgb.DMatrix
 #' @export
 dimnames.xgb.DMatrix <- function(x) {
-  attr(x, '.Dimnames')
+  fn <- getinfo(x, "feature_name")
+  ## row names is null.
+  list(NULL, fn)
 }
 
 #' @rdname dimnames.xgb.DMatrix
@@ -155,13 +160,13 @@ dimnames.xgb.DMatrix <- function(x) {
   if (!is.null(value[[1L]]))
     stop("xgb.DMatrix does not have rownames")
   if (is.null(value[[2]])) {
-    attr(x, '.Dimnames') <- NULL
+    setinfo(x, "feature_name", NULL)
     return(x)
   }
-  if (ncol(x) != length(value[[2]]))
+  if (ncol(x) != length(value[[2]])) {
-    stop("can't assign ", length(value[[2]]), " colnames to a ",
+    stop("can't assign ", length(value[[2]]), " colnames to a ", ncol(x), " column xgb.DMatrix")
-         ncol(x), " column xgb.DMatrix")
+  }
-  attr(x, '.Dimnames') <- value
+  setinfo(x, "feature_name", value[[2]])
   x
 }
 
@@ -205,11 +210,15 @@ getinfo.xgb.DMatrix <- function(object, name, ...) {
   if (typeof(name) != "character" ||
         length(name) != 1 ||
         !name %in% c('label', 'weight', 'base_margin', 'nrow',
-                   'label_lower_bound', 'label_upper_bound')) {
+                     'label_lower_bound', 'label_upper_bound', "feature_type", "feature_name")) {
-    stop("getinfo: name must be one of the following\n",
+    stop(
-         "    'label', 'weight', 'base_margin', 'nrow', 'label_lower_bound', 'label_upper_bound'")
+      "getinfo: name must be one of the following\n",
+      "    'label', 'weight', 'base_margin', 'nrow', 'label_lower_bound', 'label_upper_bound', 'feature_type', 'feature_name'"
+    )
   }
-  if (name != "nrow"){
+  if (name == "feature_name" || name == "feature_type") {
+    ret <- .Call(XGDMatrixGetStrFeatureInfo_R, object, name)
+  } else if (name != "nrow"){
     ret <- .Call(XGDMatrixGetInfo_R, object, name)
   } else {
     ret <- nrow(object)
@@ -294,6 +303,30 @@ setinfo.xgb.DMatrix <- function(object, name, info, ...) {
     .Call(XGDMatrixSetInfo_R, object, name, as.numeric(info))
     return(TRUE)
   }
+
+  set_feat_info <- function(name) {
+    msg <- sprintf(
+      "The number of %s must equal to the number of columns in the input data. %s vs. %s",
+      name,
+      length(info),
+      ncol(object)
+    )
+    if (!is.null(info)) {
+      info <- as.list(info)
+      if (length(info) != ncol(object)) {
+        stop(msg)
+      }
+    }
+    .Call(XGDMatrixSetStrFeatureInfo_R, object, name, info)
+  }
+  if (name == "feature_name") {
+    set_feat_info("feature_name")
+    return(TRUE)
+  }
+  if (name == "feature_type") {
+    set_feat_info("feature_type")
+    return(TRUE)
+  }
   stop("setinfo: unknown info name ", name)
   return(FALSE)
 }

R-package/src/init.c

@@ -42,10 +42,12 @@ extern SEXP XGDMatrixCreateFromCSR_R(SEXP, SEXP, SEXP, SEXP, SEXP);
 extern SEXP XGDMatrixCreateFromFile_R(SEXP, SEXP);
 extern SEXP XGDMatrixCreateFromMat_R(SEXP, SEXP, SEXP);
 extern SEXP XGDMatrixGetInfo_R(SEXP, SEXP);
+extern SEXP XGDMatrixGetStrFeatureInfo_R(SEXP, SEXP);
 extern SEXP XGDMatrixNumCol_R(SEXP);
 extern SEXP XGDMatrixNumRow_R(SEXP);
 extern SEXP XGDMatrixSaveBinary_R(SEXP, SEXP, SEXP);
 extern SEXP XGDMatrixSetInfo_R(SEXP, SEXP, SEXP);
+extern SEXP XGDMatrixSetStrFeatureInfo_R(SEXP, SEXP, SEXP);
 extern SEXP XGDMatrixSliceDMatrix_R(SEXP, SEXP);
 extern SEXP XGBSetGlobalConfig_R(SEXP);
 extern SEXP XGBGetGlobalConfig_R();
@@ -78,10 +80,12 @@ static const R_CallMethodDef CallEntries[] = {
   {"XGDMatrixCreateFromFile_R",   (DL_FUNC) &XGDMatrixCreateFromFile_R,   2},
   {"XGDMatrixCreateFromMat_R",    (DL_FUNC) &XGDMatrixCreateFromMat_R,    3},
   {"XGDMatrixGetInfo_R",          (DL_FUNC) &XGDMatrixGetInfo_R,          2},
+  {"XGDMatrixGetStrFeatureInfo_R", (DL_FUNC) &XGDMatrixGetStrFeatureInfo_R, 2},
   {"XGDMatrixNumCol_R",           (DL_FUNC) &XGDMatrixNumCol_R,           1},
   {"XGDMatrixNumRow_R",           (DL_FUNC) &XGDMatrixNumRow_R,           1},
   {"XGDMatrixSaveBinary_R",       (DL_FUNC) &XGDMatrixSaveBinary_R,       3},
   {"XGDMatrixSetInfo_R",          (DL_FUNC) &XGDMatrixSetInfo_R,          3},
+  {"XGDMatrixSetStrFeatureInfo_R", (DL_FUNC) &XGDMatrixSetStrFeatureInfo_R, 3},
   {"XGDMatrixSliceDMatrix_R",     (DL_FUNC) &XGDMatrixSliceDMatrix_R,     2},
   {"XGBSetGlobalConfig_R",        (DL_FUNC) &XGBSetGlobalConfig_R,        1},
   {"XGBGetGlobalConfig_R",        (DL_FUNC) &XGBGetGlobalConfig_R,        0},

R-package/src/xgboost_R.cc

@@ -249,15 +249,53 @@ XGB_DLL SEXP XGDMatrixSetInfo_R(SEXP handle, SEXP field, SEXP array) {
   return R_NilValue;
 }
 
+XGB_DLL SEXP XGDMatrixSetStrFeatureInfo_R(SEXP handle, SEXP field, SEXP array) {
+  R_API_BEGIN();
+  size_t len{0};
+  if (!isNull(array)) {
+    len = length(array);
+  }
+
+  const char *name = CHAR(asChar(field));
+  std::vector<std::string> str_info;
+  for (size_t i = 0; i < len; ++i) {
+    str_info.emplace_back(CHAR(asChar(VECTOR_ELT(array, i))));
+  }
+  std::vector<char const*> vec(len);
+  std::transform(str_info.cbegin(), str_info.cend(), vec.begin(),
+                 [](auto const &str) { return str.c_str(); });
+  CHECK_CALL(XGDMatrixSetStrFeatureInfo(R_ExternalPtrAddr(handle), name, vec.data(), len));
+  R_API_END();
+  return R_NilValue;
+}
+
+XGB_DLL SEXP XGDMatrixGetStrFeatureInfo_R(SEXP handle, SEXP field) {
+  SEXP ret;
+  R_API_BEGIN();
+  char const **out_features{nullptr};
+  bst_ulong len{0};
+  const char *name = CHAR(asChar(field));
+  XGDMatrixGetStrFeatureInfo(R_ExternalPtrAddr(handle), name, &len, &out_features);
+
+  if (len > 0) {
+    ret = PROTECT(allocVector(STRSXP, len));
+    for (size_t i = 0; i < len; ++i) {
+      SET_STRING_ELT(ret, i, mkChar(out_features[i]));
+    }
+  } else {
+    ret = PROTECT(R_NilValue);
+  }
+  R_API_END();
+  UNPROTECT(1);
+  return ret;
+}
+
 XGB_DLL SEXP XGDMatrixGetInfo_R(SEXP handle, SEXP field) {
   SEXP ret;
   R_API_BEGIN();
   bst_ulong olen;
   const float *res;
-  CHECK_CALL(XGDMatrixGetFloatInfo(R_ExternalPtrAddr(handle),
+  CHECK_CALL(XGDMatrixGetFloatInfo(R_ExternalPtrAddr(handle), CHAR(asChar(field)), &olen, &res));
-                                   CHAR(asChar(field)),
-                                 &olen,
-                                 &res));
   ret = PROTECT(allocVector(REALSXP, olen));
   for (size_t i = 0; i < olen; ++i) {
     REAL(ret)[i] = res[i];

R-package/tests/testthat/test_dmatrix.R

@@ -42,6 +42,20 @@ test_that("xgb.DMatrix: saving, loading", {
   dtest4 <- xgb.DMatrix(tmp_file, silent = TRUE)
   expect_equal(dim(dtest4), c(3, 4))
   expect_equal(getinfo(dtest4, 'label'), c(0, 1, 0))
+
+  # check that feature info is saved
+  data(agaricus.train, package = 'xgboost')
+  dtrain <- xgb.DMatrix(data = agaricus.train$data, label = agaricus.train$label)
+  cnames <- colnames(dtrain)
+  expect_equal(length(cnames), 126)
+  tmp_file <- tempfile('xgb.DMatrix_')
+  xgb.DMatrix.save(dtrain, tmp_file)
+  dtrain <- xgb.DMatrix(tmp_file)
+  expect_equal(colnames(dtrain), cnames)
+
+  ft <- rep(c("c", "q"), each=length(cnames)/2)
+  setinfo(dtrain, "feature_type", ft)
+  expect_equal(ft, getinfo(dtrain, "feature_type"))
 })
 
 test_that("xgb.DMatrix: getinfo & setinfo", {