Added hybrid CSWD index

DESCRIPTION

@@ -1,6 +1,6 @@
 Package: gpindex
 Title: Generalized Price and Quantity Indexes
-Version: 0.6.1.9002
+Version: 0.6.1.9003
 Authors@R: c(
     person("Steve", "Martin", role = c("aut", "cre", "cph"),
     email = "[email protected]",

R/price_indexes.R

@@ -13,7 +13,7 @@ pythagorean_index <- function(r) {
       "Carli", "Dutot", "Laspeyres",
       "Palgrave", "Drobisch", "Unnamed",
       "Walsh1", "MarshallEdgeworth", "GearyKhamis",
-      "Lowe", "Young"
+      "Lowe", "Young", "HybridCSWD"
     )
   )
   gen_mean <- generalized_mean(r)
@@ -60,6 +60,9 @@ pythagorean_index <- function(r) {
       },
       Young = function(p1, p0, pb, qb, na.rm = FALSE) {
         gen_mean(p1 / p0, weights(pb, qb), na.rm)
+      },
+      HybridCSWD = function(p1, p0, na.rm = FALSE) {
+        gen_mean(p1 / p0, weights(p1, p0), na.rm)
       }
     )
   }
@@ -90,6 +93,7 @@ pythagorean_index <- function(r) {
 #' - Rao
 #' - Lowe
 #' - Young
+#' - Hybrid-CSWD
 #'
 #' The weights need not sum to 1, as this normalization isn't always
 #' appropriate (i.e., for the Vartia-I weights).
@@ -103,15 +107,29 @@ pythagorean_index <- function(r) {
 #'
 #' @note
 #' Naming for the indexes and weights generally follows the CPI manual (2020),
-#' Balk (2008), and Selvanathan and Rao (1994). In several cases two or more
-#' names correspond to the same weights (e.g., Paasche and Palgrave, or
-#' Sato-Vartia and Vartia-II). The calculations are given in the examples.
+#' Balk (2008), von der Lippe (2007), and Selvanathan and Rao (1994). In several
+#' cases two or more names correspond to the same weights (e.g., Paasche and
+#' Palgrave, or Sato-Vartia and Vartia-II). The calculations are given in the
+#' examples.
 #'
 #' @seealso
 #' [update_weights()] for price-updating weights.
 #'
 #' [quantity_index()] to remap the arguments in these functions for a
 #' quantity index.
+#' 
+#' @references
+#' Balk, B. M. (2008). *Price and Quantity Index Numbers*.
+#' Cambridge University Press.
+#'
+#' IMF, ILO, Eurostat, UNECE, OECD, and World Bank. (2020).
+#' *Consumer Price Index Manual: Concepts and Methods*.
+#' International Monetary Fund.
+#'
+#' von der Lippe, P. (2007). *Index Theory and Price Statistics*. Peter Lang.
+#'
+#' Selvanathan, E. A. and Rao, D. S. P. (1994).
+#' *Index Numbers: A Stochastic Approach*. MacMillan.
 #'
 #' @examples
 #' p0 <- price6[[2]]
@@ -227,6 +245,10 @@ pythagorean_index <- function(r) {
 #' # Young
 #'
 #' all.equal(index_weights("Young")(pb, qb), pb * qb)
+#' 
+#' # Hybrid CSWD (to approximate a CSWD index)
+#' 
+#' all.equal(index_weights("HybridCSWD")(p1, p0), sqrt(p0 / p1))
 #'
 #' @family price index functions
 #' @export
@@ -239,7 +261,7 @@ index_weights <- function(
       "Walsh1", "Walsh2", "MarshallEdgeworth",
       "GearyKhamis", "Vartia1", "MontgomeryVartia",
       "Vartia2", "SatoVartia", "Theil", "Rao",
-      "Lowe", "Young"
+      "Lowe", "Young", "HybridCSWD"
     )) {
   switch(match.arg(type),
     Carli = ,
@@ -293,7 +315,8 @@ index_weights <- function(
       w0 <- scale_weights(p0 * q0)
       w1 <- scale_weights(p1 * q1)
       w0 * w1 / (w0 + w1)
-    }
+    },
+    HybridCSWD = function(p1, p0) sqrt(p0 / p1)
   )
 }
 
@@ -318,6 +341,7 @@ index_weights <- function(
 #' - Geary-Khamis
 #' - Lowe
 #' - Young
+#' - Hybrid-CSWD
 #' - **Geometric indexes**
 #' - Jevons
 #' - Geometric Laspeyres (or Jöhr)
@@ -348,11 +372,12 @@ index_weights <- function(
 #' functions.
 #'
 #' In addition to these indexes, there are also functions for calculating a
-#' variety of indexes not based on generalized means. The Fisher index is the
+#' variety of indexes based on nested generalized means. The Fisher index is the
 #' geometric mean of the arithmetic Laspeyres and Paasche indexes; the Harmonic
-#' Laspeyres Paasche index is the harmonic analog of the Fisher index (8054 on
-#' Fisher's list). The Carruthers-Sellwood-Ward-Dalen and
-#' Carruthers-Sellwood-Ward-Dalen-Balk indexes are sample analogs of the Fisher
+#' Laspeyres Paasche (or Harmonic Paasche Laspeyres) index is the harmonic
+#' analog of the Fisher index (8054 on Fisher's list). The
+#' Carruthers-Sellwood-Ward-Dalen and Carruthers-Sellwood-Ward-Dalen-Balk
+#' indexes are sample analogs of the Fisher
 #' index; the Balk-Walsh index is the sample analog of the Walsh index. The AG
 #' mean index is the arithmetic or geometric mean of the geometric and
 #' arithmetic Laspeyres indexes, weighted by the elasticity of substitution.
@@ -463,9 +488,7 @@ index_weights <- function(
 #'
 #' all.equal(
 #'   scale_weights(index_weights("HybridLaspeyres")(p1, q0)),
-#'   scale_weights(
-#'     transmute_weights(1, -1)(p1 / p0, index_weights("Laspeyres")(p0, q0))
-#'   )
+#'   transmute_weights(1, -1)(p1 / p0, index_weights("Laspeyres")(p0, q0))
 #' )
 #'
 #' # This strategy can be used to make more exotic indexes, like the

tests/Examples/gpindex-Ex.Rout.save

@@ -851,7 +851,12 @@ Warning in back_period(period) :
 > 
 > all.equal(index_weights("Young")(pb, qb), pb * qb)
 [1] TRUE
-> 
+>
+> # Hybrid CSWD (to approximate a CSWD index)
+>
+> all.equal(index_weights("HybridCSWD")(p1, p0), sqrt(p0 / p1))
+[1] TRUE
+>
 > 
 > 
 > 
@@ -1188,9 +1193,7 @@ t5   1.6720 1.0712    1.2477             0.9801 1.1850  1.2540  1.2678 0.9770
 > 
 > all.equal(
 +   scale_weights(index_weights("HybridLaspeyres")(p1, q0)),
-+   scale_weights(
-+     transmute_weights(1, -1)(p1 / p0, index_weights("Laspeyres")(p0, q0))
-+   )
++   transmute_weights(1, -1)(p1 / p0, index_weights("Laspeyres")(p0, q0))
 + )
 [1] TRUE
 > 

tests/testthat/test-price-indexes.R

@@ -36,6 +36,8 @@ test_that("arithmetic indexes work", {
                sum(p1 * qb) / sum(p0 * qb))
   expect_equal(arithmetic_index("Young")(p1, p0, pb, qb),
                weighted.mean(p1 / p0, pb * qb / sum(pb * qb)))
+  expect_equal(arithmetic_index("HybridCSWD")(p1, p0),
+               sum(sqrt(p1 / p0)) / sum(sqrt(p0 / p1)))
 })
 
 test_that("geometric indexes work", {