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diff --git a/tests/gen_true_values.R b/tests/gen_true_values.R
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+#!/usr/bin/env Rscript
+#
+# Copyright 2015 Google Inc. All rights reserved.
+# 
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+# 
+#     http://www.apache.org/licenses/LICENSE-2.0
+# 
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+source('tests/gen_counts.R')
+
+# Usage:
+#
+# $ ./gen_true_values.R exp 100 10000 1 foo.csv
+#
+# Inputs:
+#   distribution name
+#   size of the distribution's support
+#   number of clients
+#   reports per client
+#   name of the output file
+# Output:
+#   csv file with reports sampled according to the specified distribution. 
+
+GenerateTrueValues <- function(distr, distr_range, num_clients,
+                            reports_per_client, num_cohorts) {
+
+  # Sums to 1.0, e.g. [0.2 0.2 0.2 0.2 0.2] for uniform distribution of 5.
+  pdf <- ComputePdf(distr, distr_range)
+
+  num_reports <- num_clients * reports_per_client
+
+  # Computes the number of clients reporting each value, where the numbers are
+  # sampled according to pdf.  (sums to num_reports)
+  partition <- RandomPartition(num_reports, pdf)
+  
+  value_ints <- rep(1:distr_range, partition)  # expand partition
+
+  stopifnot(length(value_ints) == num_reports)
+
+  # Shuffle values randomly (may take a few sec for > 10^8 inputs)
+  value_ints <- sample(value_ints)
+
+  # Reported values are strings, so prefix integers "v". Even slower than
+  # shuffling.
+  values <- sprintf("v%d", value_ints)
+
+  # e.g. [1 1 2 2 3 3] if num_clients is 3 and reports_per_client is 2
+  client_ints <- rep(1:num_clients, each = reports_per_client)
+
+  # Cohorts are assigned to clients. Cohorts are 0-based.
+  cohorts <- client_ints %% num_cohorts  # %% is integer modulus
+
+  clients <- sprintf("c%d", client_ints)
+
+  data.frame(client = clients, cohort = cohorts, value = values)
+}
+
+main <- function(argv) {
+  distr <- argv[[1]]
+  distr_range <- as.integer(argv[[2]])
+  num_clients <- as.integer(argv[[3]])
+  reports_per_client <- as.integer(argv[[4]])
+  num_cohorts <- as.integer(argv[[5]])
+  out_file <- argv[[6]]
+
+  reports <- GenerateTrueValues(distr, distr_range, num_clients,
+                                reports_per_client, num_cohorts)
+
+  write.csv(reports, file = out_file, row.names = FALSE, quote = FALSE)
+}
+
+if (length(sys.frames()) == 0) {
+  main(commandArgs(TRUE))
+}