From 309c5d8f7ff8c36235222d079955cd3783bb7ad0 Mon Sep 17 00:00:00 2001
From: wukong <wukong@longaeva>
Date: Mon, 18 Dec 2023 12:37:31 -0800
Subject: Added a partially working function performing LU decomposition on a
 square matrix, ludcmp.awk. This is providing correct answers on _some_ test
 data, further testing debugging required here.

---
 det.awk | 57 +++++++++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 57 insertions(+)
 create mode 100644 det.awk

(limited to 'det.awk')

diff --git a/det.awk b/det.awk
new file mode 100644
index 0000000..b3e5c1f
--- /dev/null
+++ b/det.awk
@@ -0,0 +1,57 @@
+#!/usr/bin/awk -f
+
+### det.awk
+# determinant via LU
+# input: square array as delimited text
+# output: (scalar) determinant
+
+BEGIN {
+    OFS = "\t"
+    sign = "[+-]?"
+    decimal = "[0-9]+[.]?[0-9]*"
+    fraction = "[.][0-9]*"
+    exponent = "([Ee]" sign "[0-9]+)?"
+    number = "^" sign "(" decimal "|" fraction ")" exponent "$"
+}
+
+NR == 1 {
+    for (y=1; y<=NF; y++)
+        ($y ~ number) ? header[y] = "col" y : header[y] = $y
+}
+
+NF > 0 {
+    (NF > nf_max) ? nf_max = NF : nf_max = nf_max
+
+    ### columns
+    for (y=1; y<=nf_max; y++) {
+        ### rows
+        if ($y !~ number) {
+            continue
+        }
+        else {
+            read_data[NR,y] = $y
+            col_sum[y] += $y
+            row_sum[NR] += $y
+        }
+    }
+}
+
+END {
+    print length(row_sum), length(col_sum)
+    ### columns
+    for (y=1; y<=nf_max; y++) {
+        if (y in col_sum) {
+            ### rows
+            for (x=1; x<=NR; x++) {
+                if (x in row_sum) {
+                    printf("[" OFMT "," OFMT "]" OFS OFMT OFS OFMT,
+                        x, y, read_data[x,y], col_sum[y])
+                    if (x < nf_max)
+                        printf(OFS)
+                }
+            }
+        }
+        printf(ORS)
+    }
+}
+
-- 
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