From 545cbe9bda410fae30d1901027a68956b72f4173 Mon Sep 17 00:00:00 2001
From: Michael Friendly <friendly@yorku.ca>
Date: Thu, 1 Aug 2024 22:27:34 -0400
Subject: [PATCH] add JF: dev/symbolicMatrix.R

---
 dev/symbolicMatrix.R       | 98 ++++++++++++++++++++++++++++++++++++++
 dev/test-symbolic-matrix.R | 18 +++++++
 2 files changed, 116 insertions(+)
 create mode 100644 dev/symbolicMatrix.R
 create mode 100644 dev/test-symbolic-matrix.R

diff --git a/dev/symbolicMatrix.R b/dev/symbolicMatrix.R
new file mode 100644
index 00000000..53c860d9
--- /dev/null
+++ b/dev/symbolicMatrix.R
@@ -0,0 +1,98 @@
+symbolicMatrix <- function(symbol="x", nrow="m", ncol="n", matrix="pmatrix",
+                           diag=FALSE){
+  
+  # Args:
+  #   symbol: for matrix elements, character string
+  #   nrow: number of rows, can be a character
+  #   ncol: number of columns, can be a character
+  #   matrix: LaTeX matix environment
+  #   diag: if TRUE, off-diagonal elements are all 0 (and nrow must == ncol)
+  
+  row.elements <- c(symbol, symbol, "\\cdots", symbol)
+  col.subscripts <- c("1", "2", "", ncol)
+  left.sub <- c("_{", "_{", "", "_{")
+  right.sub <- c("}", "}", "", "}")
+  post.element <- c(" & ", " & ", " & ", " \\\\ \n")
+  result <- paste0("\\begin{", matrix, "} \n")
+  
+  if (diag){
+    if (nrow != ncol) stop("nrow and ncol must be the same if diag = TRUE")
+    if (is.numeric(nrow)){
+      mat <- matrix("0", nrow, nrow)
+      diag(mat) <- paste0(symbol, "_{", 1:nrow, "}")
+    } else {
+      mat <- matrix("0", 4, 4)
+      mat[3, ] <- "\\vdots"
+      mat[, 3] <- "\\cdots"
+      mat[3, 3] <- "\\ddots"
+      mat[cbind(c(1, 2, 4), c(1, 2, 4))] <- paste0(symbol, 
+                                                   c("_1", "_2", paste0("_{", nrow, "}")))
+    }
+    if (is.character(nrow)) nrow <- 4
+    for (i in 1:nrow){
+      result <- paste0(result, "  ")
+      for (j in 1:nrow){
+        result <- paste0(result, mat[i, j], if (j == nrow) " \\\\ \n" else " & ")
+      }
+    }
+  } else if (is.character(nrow)){
+    vdots <- paste0("\\vdots", 
+                    paste(rep(" ", nchar(symbol) - 1), collapse = ""))
+    row.subscripts <- c("1", "2", "", nrow)
+    if (is.character(ncol)){
+      vdots <- paste0(vdots, " & ", vdots, " & ", 
+                      if (nrow != ncol) "       & " else "\\ddots & ", 
+                      vdots, " \\\\ \n")
+      for (i in 1:4){
+        result <- paste0(result, "  ")
+        if (i == 3){
+          result <- paste0(result, vdots)
+          next
+        }
+        for (j in 1:4){
+          result <- paste0(result, row.elements[j], left.sub[j], 
+                           if (j !=3) row.subscripts[i], 
+                           col.subscripts[j],
+                           right.sub[j], post.element[j])
+        }
+      }
+    } else {
+      vdots <- paste0(paste(rep(vdots, ncol), collapse = " & "), " \\\\ \n")
+      for (i in 1:4){
+        result <- paste0(result, "  ")
+        if (i == 3){
+          result <- paste0(result, vdots)
+          next
+        }
+        for (j in 1:ncol){
+          result <- paste0(result,
+                           paste0(symbol, "_{", row.subscripts[i], if (ncol > 1) j, "}",
+                                  if (j == ncol) " \\\\ \n" else " & ")
+          )
+        }
+      }
+    }
+  } else if (is.character(ncol)){
+      for (i in 1:nrow){
+        result <- paste0(result, "  ")
+        for (j in 1:4){
+          result <- paste0(result, row.elements[j], left.sub[j], 
+                           if (j !=3 && nrow > 1) i, 
+                           col.subscripts[j],
+                           right.sub[j], post.element[j])
+        }
+      }
+    } else {
+      for (i in 1:nrow){
+        result <- paste0(result, "  ")
+        for (j in 1:ncol){
+          result <- paste0(result, symbol, "_{", if (nrow > 1) i, 
+                           if (ncol > 1) j, "}",
+                           if (j == ncol) " \\\\ \n" else " & ")
+        }
+      }
+    }
+  result <- paste0(result, "\\end{", matrix, "} \n")
+  cat(result)
+  invisible(result)
+}
diff --git a/dev/test-symbolic-matrix.R b/dev/test-symbolic-matrix.R
new file mode 100644
index 00000000..eb46a0bd
--- /dev/null
+++ b/dev/test-symbolic-matrix.R
@@ -0,0 +1,18 @@
+# test symbolicMatrix
+
+source(here::here("dev", "symbolicMatrix.R"))
+
+symbolicMatrix()
+symbolicMatrix("\\beta")
+symbolicMatrix(nrow="n", ncol="n")
+symbolicMatrix(ncol=3)
+symbolicMatrix(nrow=4)
+symbolicMatrix(nrow=4, ncol=4)
+symbolicMatrix(nrow=1)
+symbolicMatrix(ncol=1)
+symbolicMatrix(nrow=1, ncol=4)
+symbolicMatrix(nrow=3, ncol=1)
+
+symbolicMatrix(nrow=3, ncol=3, diag=TRUE)
+symbolicMatrix(nrow="n", ncol="n", diag=TRUE)
+