From 919d5884cd0c0061f733a5070a6677a198ed4732 Mon Sep 17 00:00:00 2001
From: Pierre-Edouard Portier <p6e7p7@freeshell.org>
Date: Wed, 18 Jan 2023 16:32:24 +0100
Subject: [PATCH] factorization of onehot encoding in a function

---
 05_d_svd_mca_code.R | 50 +++++++++++++++++++++++++++------------------
 1 file changed, 30 insertions(+), 20 deletions(-)

diff --git a/05_d_svd_mca_code.R b/05_d_svd_mca_code.R
index fc09674..51809c1 100644
--- a/05_d_svd_mca_code.R
+++ b/05_d_svd_mca_code.R
@@ -121,8 +121,7 @@ function()
   levels(dat$c_house_value) <- c('HV:A', 'HV:B', 'HV:C', 'HV:D', 'HV:E')
 
   # création du jeu de données quantifié
-  dat.all <- dat
-  dat <- dat.all[c('ocean_proximity', 'c_longitude', 'c_latitude', 'c_age',
+  dat <- dat[c('ocean_proximity', 'c_longitude', 'c_latitude', 'c_age',
                    'c_rooms', 'c_bedrooms', 'c_pop', 'c_households', 'c_income',
                    'c_house_value')]
   vent <- list()
@@ -146,36 +145,47 @@ function()
   dat <- droplevels(dat)
 
   # positionnement de c_house_value en variable supplémentaire
-  supind <- which(names(dat) == "c_house_value")
+  supvar <- which(names(dat) == "c_house_value")
 
-  r <- list( vent=vent, dat=dat, supind=supind )
+  r <- list( vent=vent, dat=dat, supvar=supvar )
 
   return(r)
 }
 
+# one hot encoding (codage disjonctif complet) of a dataframe
+# made of categorical variables
+onehot_enc <-
+function(dat.cat)
+{
+  if(!all(as.logical(lapply(dat.cat, is.factor)))) {
+    warning("All variables must be factors.")
+    return(invisible(NULL))
+  }
+  lev_n <- unlist(lapply(dat.cat, nlevels))
+  n <- cumsum(lev_n)
+  J_t <- sum(lev_n)
+  Q_t <- dim(dat.cat)[2]
+  I <- dim(dat.cat)[1]
+  Z <- matrix(0, nrow = I, ncol = J_t)
+  numdat <- lapply(dat.cat, as.numeric)
+  offset <- c(0, n[-length(n)])
+  for (i in 1:Q_t) Z[1:I + (I * (offset[i] + numdat[[i]] - 1))] <- 1
+  dimnames(Z)[[1]] <- as.character(1:I)
+  dimnames(Z)[[2]] <- as.character(unlist(lapply(dat.cat, levels)))
+  return(Z)
+}
+
 mca <-
 function(dat, nclst = 100)
 {
-  lev_n <- unlist(lapply(dat$dat, nlevels))
-  n <- cumsum(lev_n)
-  J_t <- sum(lev_n)
-  Q_t <- dim(dat$dat)[2]
-  I <- dim(dat$dat)[1]
-
   # Indicator matrix
-  Z <- matrix(0, nrow = I, ncol = J_t)
-  numdat <- lapply(dat$dat, as.numeric)
-  offset <- c(0, n[-length(n)])
-  for (i in 1:Q_t)
-    Z[1:I + (I * (offset[i] + numdat[[i]] - 1))] <- 1
-  dimnames(Z)[[1]] <- as.character(1:I)
-  dimnames(Z)[[2]] <- as.character(unlist(lapply(dat$dat, levels)))
-  Z_sup_min <- n[dat$supind[1] - 1] + 1
-  Z_sup_max <- n[dat$supind[length(dat$supind)]]
+  Z <- onehot_enc(dat$dat)
+  Z_sup_min <- n[dat$supvar[1] - 1] + 1
+  Z_sup_max <- n[dat$supvar[length(dat$supvar)]]
   Z_sup_ind <- Z_sup_min : Z_sup_max
   Z_act <- Z[,-Z_sup_ind]
   J <- dim(Z_act)[2]
-  Q <- dim(dat$dat)[2] - length(dat$supind)
+  Q <- dim(dat$dat)[2] - length(dat$supvar)
 
   # Burt matrix
   B <- t(Z_act) %*% Z_act