[r] add tf-idf and log normalization functions

r/NAMESPACE

@@ -65,6 +65,8 @@ export(min_by_row)
 export(min_scalar)
 export(multiply_cols)
 export(multiply_rows)
+export(normalize_log)
+export(normalize_tfidf)
 export(nucleosome_counts)
 export(open_fragments_10x)
 export(open_fragments_dir)

r/NEWS.md

@@ -22,6 +22,7 @@ Contributions welcome :)
 - Add `rowQuantiles()` and `colQuantiles()` functions, which return the quantiles of each row/column of a matrix. Currently `rowQuantiles()` only works on row-major matrices and `colQuantiles()` only works on col-major matrices.
   If `matrixStats` or `MatrixGenerics` packages are installed, `BPCells::colQuantiles()` will fall back to their implementations for non-BPCells objects. (pull request #128)
 - Add `pseudobulk_matrix()` which allows pseudobulk aggregation by `sum` or `mean` and calculation of per-pseudobulk `variance` and `nonzero` statistics for each gene (pull request #128)
+- Add functions `normalize_tfidf()` and `normalize_log()`, which allow for easy normalization of iterable matrices using TF-IDF or log1p(pull request #168)
 
 ## Improvements
 - `trackplot_loop()` now accepts discrete color scales

r/R/transforms.R

@@ -923,3 +923,57 @@ regress_out <- function(mat, latent_data, prediction_axis = c("row", "col")) {
     vars_to_regress = vars_to_regress
   )
 }
+
+#################
+# Normalizations
+#################
+
+#' Normalize a matrix using log normalization
+#' @param mat (IterableMatrix) Matrix to normalize
+#' @param scale_factor (numeric) Scale factor to multiply matrix by for log normalization
+#' @param add_one (logical) Add one to the matrix before log normalization
+#' @returns log normalized matrix.
+#' @export
+normalize_log <- function(mat, scale_factor = 1e4, add_one = TRUE) {
+  assert_is(mat, "IterableMatrix")
+  assert_is_numeric(scale_factor)
+  assert_true(is.logical(add_one))
+  assert_greater_than_zero(scale_factor)
+  mat <- mat * scale_factor
+  if (!add_one) mat <- mat - 1 
+  return(log1p(mat))
+}
+
+
+#' Normalize a `(features x cells)`` matrix using term frequency-inverse document frequency
+#' @param mat (IterableMatrix) to normalize
+#' @param feature_means (numeric) Means of the features to normalize by.  If no names are provided, then 
+#' each numeric value is assumed to correspond to the feature mean for the corresponding row of the matrix.
+#' Else, map each feature name to its mean value.
+#' @returns tf-idf normalized matrix.
+#' @export
+normalize_tfidf <- function(mat, feature_means = NULL, threads = 1L) {
+  assert_is(mat, "IterableMatrix")
+  assert_is_wholenumber(threads)
+  # If feature means are passed in, only need to calculate term frequency
+  if (is.null(feature_means)) {
+    mat_stats <- matrix_stats(mat, row_stats = c("mean"), col_stats = c("mean"))
+    feature_means <- mat_stats$row_stats["mean", ]
+    read_depth <- mat_stats$col_stats["mean", ] * nrow(mat)
+  } else {
+    assert_is_numeric(feature_means)
+    if (!is.null(names(feature_means)) && !is.null(rownames(mat))) {
+      # Make sure every name in feature means exists in rownames(mat)
+      # In the case there is a length mismatch but the feature names all exist in feature_means
+      # will not error out
+      assert_true(all(rownames(mat) %in% names(feature_means)))
+      feature_means <- feature_means[rownames(mat)]
+    } else {
+      assert_len(feature_means, nrow(mat))
+    }
+    read_depth <- matrix_stats(mat, col_stats = c("mean"), threads = threads)$col_stats["mean",] * nrow(mat)
+  }
+  tf <- mat %>% multiply_cols(1 / read_depth)
+  idf <- 1 / feature_means
+  return(tf %>% multiply_rows(idf))
+}

r/pkgdown/_pkgdown.yml

@@ -126,6 +126,8 @@ reference:
   - checksum
   - apply_by_row
   - regress_out
+  - normalize_log
+  - normalize_tfidf
   - IterableMatrix-methods
   - pseudobulk_matrix
 

r/tests/testthat/test-matrix_transforms.R

@@ -346,3 +346,49 @@ test_that("linear regression works", {
     expect_equal(as(m1, "matrix"), ans)
     expect_equal(as(m1t, "matrix"), ans)
 })
+
+test_that("tf-idf normalization works", {
+    m <- generate_sparse_matrix(5, 5)
+    rownames(m) <- paste0("row", seq_len(nrow(m)))
+    rev_rownames <- rev(rownames(m))
+    # Create tf-idf normalization for dgCMatrix
+    res_dgc <- diag(1/rowMeans(m)) %*% (m %*% diag(1/colSums(m))) %>% as("dgCMatrix")
+
+    rownames(res_dgc) <- rownames(m)
+    m2 <- as(m, "IterableMatrix")
+    # Check that we can pass in row means as a (named) vector
+    row_means <- matrix_stats(m2, row_stats = c("mean"))$row_stats["mean",]
+    # Test that row means ordering does not matter as long as names exist
+    row_means_shuffled <- row_means[sample(1:length(row_means))]
+    # Test that row means can have an extra element as long as all rownames are in the vector
+    row_means_plus_one <- c(row_means, row6 = 1)
+
+
+    res <- normalize_tfidf(m2)
+    expect_equal(res %>% as("dgCMatrix"), res_dgc)
+    res_with_row_means <- normalize_tfidf(m2, feature_means = row_means)
+    expect_identical(res, res_with_row_means)
+
+    res_with_shuffled_row_means <- normalize_tfidf(m2, feature_means = row_means_shuffled)
+    expect_identical(res_with_row_means, res_with_shuffled_row_means, res)
+
+    res_with_row_means_with_extra_element <- normalize_tfidf(m2, feature_means = row_means_plus_one)
+    expect_identical(res, res_with_row_means_with_extra_element)
+})
+
+test_that("normalize_log works", {
+    m <- generate_sparse_matrix(5, 5)
+    m2 <- as(m, "IterableMatrix")
+    # Test that default params yield the same as log1p on dgCMatrix
+    res_1 <- as(normalize_log(m2), "dgCMatrix")
+    expect_equal(res_1, log1p(m*1e4))
+
+    # Test that changing scale factor works
+    res_2 <- as(normalize_log(m2, scale_factor = 1e5), "dgCMatrix")
+    expect_identical(res_2, log1p(m*1e5))
+    # Test that removing the add_one works
+    # log of 0 is -inf, but we don't do that on the c side, and just have really large negative numbers.
+    res_3 <- as(normalize_log(m2, add_one = FALSE), "dgCMatrix")
+    res_3@x[res_3@x < -700] <- -Inf
+    expect_identical(as(res_3, "dgeMatrix"), log(m*1e4))
+})