Initial commitmain

author: 3gg <3gg@shellblade.net> 2024-01-02 19:43:21 +0100
committer: 3gg <3gg@shellblade.net> 2024-01-02 19:43:21 +0100
commit: 8f3dadb7178a07ebadf782507cf2af5995321c71 (patch)
tree: 69081999c2845fb8d15013b3f1fde9ebe4cddf92
4 files changed, 198 insertions, 0 deletions
diff --git a/mortgage.html b/mortgage.html
new file mode 100644
index 0000000..07de66b
--- /dev/null
+++ b/mortgage.html
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+<!DOCTYPE html>
+<html>
+<head>
+    <title>Mortgage Calculator</title>
+    <style>
+        #parameters {
+            margin-top: 2em;
+            display: grid;
+            grid-template-columns: 10em min-content;
+            column-gap: 1em;
+            row-gap: 0.5em;
+        }
+        #parameters div {
+            text-align: right;
+        }
+        #parameters input {
+            width: 12em;
+            text-align: right;
+        }
+        #results {
+            margin-top: 2em;
+        }
+        #results-table {
+            border: 1px solid;
+            border-collapse: collapse;
+        }
+        #results-table th {
+            padding-top: 0.5em;
+            padding-bottom: 0.5em;
+        }
+        #results-table th, td {
+            text-align: center;
+            padding-left: 1em;
+            padding-right: 1em;
+        }
+        #results-table tr:nth-child(even){
+            background-color: #f2f2f2;
+        }
+        #results-table tr:hover {background-color: #ddd;}
+    </style>
+</head>
+<body>
+    <h1>Mortgage Calculator</h1>
+    <div id="parameters">
+        <div>Principal</div>
+        <div><input id="principal" type="number" value="100000" onchange="update()"></div>
+        <div>Annual Interest (%)</div>
+        <div><input id="interest" type="number" value="5.0" onchange="update()"></div>
+        <div>Installments</div>
+        <div><input id="installments" type="number" value="300" onchange="update()"></div>
+    </div>
+    <div id="results">
+        <table id="results-table">
+            <tr>
+                <th>Time</th>
+                <th>Outstanding Debt</th>
+                <th>Monthly Installment</th>
+                <th>Interest Paid</th>
+                <th>Amount Amortised</th>
+            </tr>
+        </table>
+    </div>
+    <script type="text/javascript" src="mortgage.js"></script>
+</body>
+</html>
diff --git a/mortgage.js b/mortgage.js
new file mode 100644
index 0000000..ffc1b1d
--- /dev/null
+++ b/mortgage.js
@@ -0,0 +1,74 @@
+/// Round up the given number two the nearest two decimal places.
+function round(x) {
+    return Math.ceil(x*100)/100;
+}
+/// Format the float as a string using two decimal places.
+function fmt(x) {
+    return round(x).toFixed(2);
+}
+/// Clear all rows in the table except for the first row (header).
+function clear_table(table) {
+    while (table.rows.length > 1) {
+        table.deleteRow(1);
+    }
+}
+/// Insert the values into a new row in the table.
+function insert_row(table, values) {
+    var row = table.insertRow(table.rows.length);
+    values.forEach((value) => {
+        row.insertCell(row.cells.length).innerHTML = value;
+    });
+}
+/// Compute the mortgage.
+function compute_mortgage(principal, annual_interest, installments, table) {
+    const p = principal;
+    const i = annual_interest / 100 / 12; // Monthly equivalent.
+    const n = installments;
+    const monthly_installment = p * (i * (1 + i)**n) / ((1 + i)**n - 1);
+    var debt = principal;
+    var total_interest = 0;
+    var total_amortised = 0;
+    clear_table(table);
+    for (k = 0; k < n; ++k) {
+        const interest = i * debt;
+        const amortised = monthly_installment - interest;
+        const values = [k.toString(), fmt(debt), fmt(monthly_installment), fmt(interest), fmt(amortised)];
+        insert_row(table, values);
+        total_interest += interest;
+        total_amortised += amortised;
+        debt -= amortised;
+    }
+    const total_interest_pct = total_interest / principal * 100;
+    insert_row(table, ["", "", "", "", ""]); // Separator.
+    insert_row(table, ["Total", "", "Amount Paid", "Interest Paid", "Amount Amortised"]);
+    insert_row(table, [
+        "",
+        "",
+        fmt(monthly_installment * n),
+        fmt(total_interest) + " (" + fmt(total_interest_pct) + "%)",
+        fmt(total_amortised)]);
+}
+function update() {
+    const principal    = parseFloat(document.getElementById("principal").value);
+    const interest     = parseFloat(document.getElementById("interest").value);
+    const installments = parseInt(document.getElementById("installments").value);
+    const results      = document.getElementById("results-table");
+    compute_mortgage(principal, interest, installments, results);
+}
+update();
diff --git a/mortgage.py b/mortgage.py
new file mode 100644
index 0000000..3b9b958
--- /dev/null
+++ b/mortgage.py
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+import argparse
+import math
+import sys
+from tabulate import tabulate, SEPARATING_LINE
+def calc_payments(principal, annual_interest, installments):
+    p = principal
+    i = annual_interest / 100 / 12 # Monthly equivalent.
+    n = installments
+    def fmt(x):
+        return f"{math.ceil(x*100)/100:.2f}"
+    table = [["Time", "Outstanding Debt", "Monthly Installment", "Interest Paid", "Amount Amortised"]]
+    monthly_installment = p * (i * (1 + i)**n) / ((1 + i)**n - 1)
+    debt = principal
+    total_interest = 0
+    total_amortised = 0
+    for k in range(n):
+        interest = i * debt
+        amortised = monthly_installment - interest
+        table.append([k] + [fmt(x) for x in [debt, monthly_installment, interest, amortised]])
+        total_interest += interest
+        total_amortised += amortised
+        debt -= amortised
+    total_interest_pct = total_interest / principal * 100
+    table.append(SEPARATING_LINE)
+    table.append(["Total", "", "Amount Paid", "Interest Paid", "Amount Amortised"])
+    table.append(["", ""] + [
+        fmt(monthly_installment * n),
+        fmt(total_interest) + f" ({fmt(total_interest_pct)}%)",
+        fmt(total_amortised)])
+    return table
+def main():
+    parser = argparse.ArgumentParser()
+    parser.add_argument("-p", "--principal", type=float, default=100000, help="Principal")
+    parser.add_argument("-i", "--interest", type=float, default=5, help="Annual interest %")
+    parser.add_argument("-n", "--installments", type=int, default=300, help="Number of installments")
+    args = parser.parse_args()
+    table = calc_payments(args.principal, args.interest, args.installments)
+    print(tabulate(table))
+    return 0
+if __name__ == "__main__":
+    sys.exit(main())
diff --git a/requirements.txt b/requirements.txt
new file mode 100644
index 0000000..a5d5159
--- /dev/null
+++ b/requirements.txt
@@ -0,0 +1 @@
+tabulate
author	3gg <3gg@shellblade.net>	2024-01-02 19:43:21 +0100
committer	3gg <3gg@shellblade.net>	2024-01-02 19:43:21 +0100
commit	8f3dadb7178a07ebadf782507cf2af5995321c71 (patch)
tree	69081999c2845fb8d15013b3f1fde9ebe4cddf92

diff --git a/mortgage.html b/mortgage.html new file mode 100644 index 0000000..07de66b --- /dev/null +++ b/mortgage.html
@@ -0,0 +1,68 @@
	1	<!DOCTYPE html>
	2	<html>
	3
	4	<head>
	5	<title>Mortgage Calculator</title>
	6	<style>
	7	#parameters {
	8	margin-top: 2em;
	9	display: grid;
	10	grid-template-columns: 10em min-content;
	11	column-gap: 1em;
	12	row-gap: 0.5em;
	13	}
	14	#parameters div {
	15	text-align: right;
	16	}
	17	#parameters input {
	18	width: 12em;
	19	text-align: right;
	20	}
	21	#results {
	22	margin-top: 2em;
	23	}
	24	#results-table {
	25	border: 1px solid;
	26	border-collapse: collapse;
	27	}
	28	#results-table th {
	29	padding-top: 0.5em;
	30	padding-bottom: 0.5em;
	31	}
	32	#results-table th, td {
	33	text-align: center;
	34	padding-left: 1em;
	35	padding-right: 1em;
	36	}
	37	#results-table tr:nth-child(even){
	38	background-color: #f2f2f2;
	39	}
	40	#results-table tr:hover {background-color: #ddd;}
	41	</style>
	42	</head>
	43
	44	<body>
	45	<h1>Mortgage Calculator</h1>
	46	<div id="parameters">
	47	<div>Principal</div>
	48	<div><input id="principal" type="number" value="100000" onchange="update()"></div>
	49	<div>Annual Interest (%)</div>
	50	<div><input id="interest" type="number" value="5.0" onchange="update()"></div>
	51	<div>Installments</div>
	52	<div><input id="installments" type="number" value="300" onchange="update()"></div>
	53	</div>
	54	<div id="results">
	55	<table id="results-table">
	56	<tr>
	57	<th>Time</th>
	58	<th>Outstanding Debt</th>
	59	<th>Monthly Installment</th>
	60	<th>Interest Paid</th>
	61	<th>Amount Amortised</th>
	62	</tr>
	63	</table>
	64	</div>
	65	<script type="text/javascript" src="mortgage.js"></script>
	66	</body>
	67
	68	</html>


diff --git a/mortgage.js b/mortgage.js new file mode 100644 index 0000000..ffc1b1d --- /dev/null +++ b/mortgage.js
@@ -0,0 +1,74 @@
	1	/// Round up the given number two the nearest two decimal places.
	2	function round(x) {
	3	return Math.ceil(x*100)/100;
	4	}
	5
	6	/// Format the float as a string using two decimal places.
	7	function fmt(x) {
	8	return round(x).toFixed(2);
	9	}
	10
	11	/// Clear all rows in the table except for the first row (header).
	12	function clear_table(table) {
	13	while (table.rows.length > 1) {
	14	table.deleteRow(1);
	15	}
	16	}
	17
	18	/// Insert the values into a new row in the table.
	19	function insert_row(table, values) {
	20	var row = table.insertRow(table.rows.length);
	21	values.forEach((value) => {
	22	row.insertCell(row.cells.length).innerHTML = value;
	23	});
	24	}
	25
	26	/// Compute the mortgage.
	27	function compute_mortgage(principal, annual_interest, installments, table) {
	28	const p = principal;
	29	const i = annual_interest / 100 / 12; // Monthly equivalent.
	30	const n = installments;
	31
	32	const monthly_installment = p * (i * (1 + i)n) / ((1 + i)n - 1);
	33
	34	var debt = principal;
	35	var total_interest = 0;
	36	var total_amortised = 0;
	37
	38	clear_table(table);
	39
	40	for (k = 0; k < n; ++k) {
	41	const interest = i * debt;
	42	const amortised = monthly_installment - interest;
	43
	44	const values = [k.toString(), fmt(debt), fmt(monthly_installment), fmt(interest), fmt(amortised)];
	45	insert_row(table, values);
	46
	47	total_interest += interest;
	48	total_amortised += amortised;
	49	debt -= amortised;
	50	}
	51
	52	const total_interest_pct = total_interest / principal * 100;
	53
	54	insert_row(table, ["", "", "", "", ""]); // Separator.
	55
	56	insert_row(table, ["Total", "", "Amount Paid", "Interest Paid", "Amount Amortised"]);
	57	insert_row(table, [
	58	"",
	59	"",
	60	fmt(monthly_installment * n),
	61	fmt(total_interest) + " (" + fmt(total_interest_pct) + "%)",
	62	fmt(total_amortised)]);
	63	}
	64
	65	function update() {
	66	const principal = parseFloat(document.getElementById("principal").value);
	67	const interest = parseFloat(document.getElementById("interest").value);
	68	const installments = parseInt(document.getElementById("installments").value);
	69	const results = document.getElementById("results-table");
	70
	71	compute_mortgage(principal, interest, installments, results);
	72	}
	73
	74	update();


diff --git a/mortgage.py b/mortgage.py new file mode 100644 index 0000000..3b9b958 --- /dev/null +++ b/mortgage.py
@@ -0,0 +1,55 @@
	1	import argparse
	2	import math
	3	import sys
	4	from tabulate import tabulate, SEPARATING_LINE
	5
	6
	7	def calc_payments(principal, annual_interest, installments):
	8	p = principal
	9	i = annual_interest / 100 / 12 # Monthly equivalent.
	10	n = installments
	11
	12	def fmt(x):
	13	return f"{math.ceil(x*100)/100:.2f}"
	14
	15	table = [["Time", "Outstanding Debt", "Monthly Installment", "Interest Paid", "Amount Amortised"]]
	16
	17	monthly_installment = p * (i * (1 + i)n) / ((1 + i)n - 1)
	18	debt = principal
	19	total_interest = 0
	20	total_amortised = 0
	21
	22	for k in range(n):
	23	interest = i * debt
	24	amortised = monthly_installment - interest
	25	table.append([k] + [fmt(x) for x in [debt, monthly_installment, interest, amortised]])
	26
	27	total_interest += interest
	28	total_amortised += amortised
	29	debt -= amortised
	30
	31	total_interest_pct = total_interest / principal * 100
	32
	33	table.append(SEPARATING_LINE)
	34	table.append(["Total", "", "Amount Paid", "Interest Paid", "Amount Amortised"])
	35	table.append(["", ""] + [
	36	fmt(monthly_installment * n),
	37	fmt(total_interest) + f" ({fmt(total_interest_pct)}%)",
	38	fmt(total_amortised)])
	39	return table
	40
	41
	42	def main():
	43	parser = argparse.ArgumentParser()
	44	parser.add_argument("-p", "--principal", type=float, default=100000, help="Principal")
	45	parser.add_argument("-i", "--interest", type=float, default=5, help="Annual interest %")
	46	parser.add_argument("-n", "--installments", type=int, default=300, help="Number of installments")
	47	args = parser.parse_args()
	48
	49	table = calc_payments(args.principal, args.interest, args.installments)
	50	print(tabulate(table))
	51	return 0
	52
	53
	54	if __name__ == "__main__":
	55	sys.exit(main())


diff --git a/requirements.txt b/requirements.txt new file mode 100644 index 0000000..a5d5159 --- /dev/null +++ b/requirements.txt
@@ -0,0 +1 @@
		tabulate