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Merge branch 'feature/41-add-median-function' into develop
Fixes #41
2 parents 4186f6e + 6372ee4 commit 0bbdeb5

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5 files changed

+156
-2
lines changed

5 files changed

+156
-2
lines changed

‎collection/665.dat‎

Lines changed: 18 additions & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -0,0 +1,18 @@
1+
function Median(A: array of Double): Double; overload;
2+
var
3+
MiddleLo: Integer;
4+
begin
5+
if System.Length(A) = 0 then
6+
raise SysUtils.EArgumentException.Create('Array is empty');
7+
// optimisations for array lengths 1 & 2 to avoid sorting
8+
if System.Length(A) = 1 then
9+
Exit(A[0]);
10+
if System.Length(A) = 2 then
11+
Exit((A[0] + A[1]) / 2.0);
12+
Generics.Collections.TArray.Sort<Double>(A); // using standard comparer
13+
MiddleLo := System.Length(A) div 2 - 1;
14+
if System.Odd(System.Length(A)) then
15+
Result := A[MiddleLo + 1]
16+
else
17+
Result := (A[MiddleLo] + A[MiddleLo + 1]) / 2.0;
18+
end;

‎collection/666.dat‎

Lines changed: 18 additions & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -0,0 +1,18 @@
1+
function Median(A: array of Integer): Double; overload;
2+
var
3+
MiddleLo: Integer;
4+
begin
5+
if System.Length(A) = 0 then
6+
raise SysUtils.EArgumentException.Create('Array is empty');
7+
// optimisations for array lengths 1 & 2 to avoid sorting
8+
if System.Length(A) = 1 then
9+
Exit(A[0]);
10+
if System.Length(A) = 2 then
11+
Exit((A[0] + A[1]) / 2);
12+
Generics.Collections.TArray.Sort<Integer>(A); // using standard comparer
13+
MiddleLo := System.Length(A) div 2 - 1;
14+
if System.Odd(Length(A)) then
15+
Result := A[MiddleLo + 1]
16+
else
17+
Result := (A[MiddleLo] + A[MiddleLo + 1]) / 2;
18+
end;

‎collection/maths.ini‎

Lines changed: 26 additions & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -1871,3 +1871,29 @@ AdvancedTest.URL="https://github.com/delphidabbler/code-snippets/tree/master/tes
18711871
Snip=664.dat
18721872
DelphiXE=Y
18731873
Delphi12A=Y
1874+
1875+
[Median_Double]
1876+
DisplayName="Median (Double overload)"
1877+
DescEx="<p>Returns the median of an array of floating point values.</p><p>Raises an <var>EArgumentException</var> exception if the array is empty.</p>"
1878+
Kind=routine
1879+
Units=SysUtils,Generics.Collections
1880+
SeeAlso=Median_Integer
1881+
TestInfo=advanced
1882+
AdvancedTest.Level=unit-tests
1883+
AdvancedTest.URL="https://github.com/delphidabbler/code-snippets/tree/master/tests/Cat-Maths"
1884+
Snip=665.dat
1885+
DelphiXE=Y
1886+
Delphi12A=Y
1887+
1888+
[Median_Integer]
1889+
DisplayName="Median (Integer overload)"
1890+
DescEx="<p>Returns the median of an array of integer values.</p><p>Raises an <var>EArgumentException</var> exception if the array is empty.</p>"
1891+
Kind=routine
1892+
Units=SysUtils,Generics.Collections
1893+
SeeAlso=Median_Double
1894+
TestInfo=advanced
1895+
AdvancedTest.Level=unit-tests
1896+
AdvancedTest.URL="https://github.com/delphidabbler/code-snippets/tree/master/tests/Cat-Maths"
1897+
Snip=666.dat
1898+
DelphiXE=Y
1899+
Delphi12A=Y

‎tests/Cat-Maths/TestUMathsCatSnippets.pas‎

Lines changed: 34 additions & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -86,6 +86,8 @@ TestMathsCatSnippets = class(TTestCase)
8686
procedure TestIsNarcissistic;
8787
procedure TestLSE; // required by SoftMax
8888
procedure TestSoftMax;
89+
procedure TestMedian_Integer;
90+
procedure TestMedian_Double;
8991
end;
9092

9193
implementation
@@ -881,6 +883,38 @@ procedure TestMathsCatSnippets.TestMaxOfArray_Single;
881883
Check(SameValue(N, MaxOfArray(A)), 'Test 5');
882884
end;
883885

886+
procedure TestMathsCatSnippets.TestMedian_Double;
887+
const
888+
Fudge = 0.000001;
889+
A1: array[1..1] of Double = (436.57);
890+
A2: array[1..2] of Double = (-123.45, 170.05);
891+
A5: array[1..5] of Double = (1.234, 4256.12345, 7000000000.0, PI, 0.000006758493);
892+
A6: array[1..6] of Double = (4883.937382, 37473.0, 235.00001, -99.9282, 42.32654, 56.986382);
893+
A7: array[1..7] of Double = (938298.0837, 729837.3627, 80001.34, 79876.46372, 67012.1234, 38983.12, 3500.93937);
894+
begin
895+
CheckTrue(SameValue(436.57, Median(A1), Fudge), '#1');
896+
CheckTrue(SameValue(23.3, Median(A2), Fudge), '#2');
897+
CheckTrue(SameValue(PI, Median(A5), Fudge), '#5');
898+
CheckTrue(SameValue(145.993196, Median(A6), Fudge), '#6');
899+
CheckTrue(SameValue(79876.46372, Median(A7), Fudge), '#7');
900+
end;
901+
902+
procedure TestMathsCatSnippets.TestMedian_Integer;
903+
const
904+
A1: array[1..1] of Integer = (4);
905+
A2: array[1..2] of Integer = (-6, 1);
906+
A5: array[1..5] of Integer = (1, 3, 5, 7, 9);
907+
A6: array[1..6] of Integer = (4883, 37473, 235, -99, 42, 56);
908+
A7: array[1..7] of Integer = (77, 66, 55, 44, 33, 22, 11);
909+
begin
910+
CheckTrue(SameValue(4.0, Median(A1)), '#1');
911+
CheckTrue(SameValue(-2.5, Median(A2)), '#2');
912+
CheckTrue(SameValue(5.0, Median(A5)), '#5');
913+
CheckTrue(SameValue(145.5, Median(A6)), '#6');
914+
CheckTrue(SameValue(44.0, Median(A7)), '#7');
915+
916+
end;
917+
884918
procedure TestMathsCatSnippets.TestMid_Double;
885919
var
886920
A, B, C, D, E: Double;

‎tests/Cat-Maths/UMathsCatSnippets.pas‎

Lines changed: 60 additions & 2 deletions
Original file line numberDiff line numberDiff line change
@@ -6,7 +6,7 @@
66
* The unit is copyright © 2005-2024 by Peter Johnson & Contributors and is
77
* licensed under the MIT License (https://opensource.org/licenses/MIT).
88
*
9-
* Generated on : Fri, 10 Jan 2025 09:52:09 GMT.
9+
* Generated on : Fri, 10 Jan 2025 19:22:03 GMT.
1010
* Generated by : DelphiDabbler CodeSnip Release 4.24.0.
1111
*
1212
* The latest version of CodeSnip is available from the CodeSnip GitHub project
@@ -18,7 +18,7 @@
1818
interface
1919

2020
uses
21-
SysUtils, Math, Types, Windows;
21+
SysUtils, Math, Types, Windows, Generics.Collections;
2222

2323
{
2424
Encapsulates a point with double precision floating point coordinates.
@@ -268,6 +268,18 @@ function MaxOfArray(const A: array of Integer): Integer; overload;
268268
}
269269
function MaxOfArray(const A: array of Single): Single; overload;
270270

271+
{
272+
Returns the median of an array of floating point values.
273+
Raises an EArgumentException exception if the array is empty.
274+
}
275+
function Median(A: array of Double): Double; overload;
276+
277+
{
278+
Returns the median of an array of integer values.
279+
Raises an EArgumentException exception if the array is empty.
280+
}
281+
function Median(A: array of Integer): Double; overload;
282+
271283
{
272284
Returns the middle of three double precision floating point values.
273285
}
@@ -1314,6 +1326,52 @@ function MaxOfArray(const A: array of Single): Single; overload;
13141326
Result := A[Idx];
13151327
end;
13161328

1329+
{
1330+
Returns the median of an array of floating point values.
1331+
Raises an EArgumentException exception if the array is empty.
1332+
}
1333+
function Median(A: array of Double): Double; overload;
1334+
var
1335+
MiddleLo: Integer;
1336+
begin
1337+
if System.Length(A) = 0 then
1338+
raise SysUtils.EArgumentException.Create('Array is empty');
1339+
// optimisations for array lengths 1 & 2 to avoid sorting
1340+
if System.Length(A) = 1 then
1341+
Exit(A[0]);
1342+
if System.Length(A) = 2 then
1343+
Exit((A[0] + A[1]) / 2.0);
1344+
Generics.Collections.TArray.Sort<Double>(A); // using standard comparer
1345+
MiddleLo := System.Length(A) div 2 - 1;
1346+
if System.Odd(System.Length(A)) then
1347+
Result := A[MiddleLo + 1]
1348+
else
1349+
Result := (A[MiddleLo] + A[MiddleLo + 1]) / 2.0;
1350+
end;
1351+
1352+
{
1353+
Returns the median of an array of integer values.
1354+
Raises an EArgumentException exception if the array is empty.
1355+
}
1356+
function Median(A: array of Integer): Double; overload;
1357+
var
1358+
MiddleLo: Integer;
1359+
begin
1360+
if System.Length(A) = 0 then
1361+
raise SysUtils.EArgumentException.Create('Array is empty');
1362+
// optimisations for array lengths 1 & 2 to avoid sorting
1363+
if System.Length(A) = 1 then
1364+
Exit(A[0]);
1365+
if System.Length(A) = 2 then
1366+
Exit((A[0] + A[1]) / 2);
1367+
Generics.Collections.TArray.Sort<Integer>(A); // using standard comparer
1368+
MiddleLo := System.Length(A) div 2 - 1;
1369+
if System.Odd(Length(A)) then
1370+
Result := A[MiddleLo + 1]
1371+
else
1372+
Result := (A[MiddleLo] + A[MiddleLo + 1]) / 2;
1373+
end;
1374+
13171375
{
13181376
Returns the middle of three double precision floating point values.
13191377
}

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