From e64775fdcc38a9bc882ef32b4d4d491ad63acbdd Mon Sep 17 00:00:00 2001
From: xuri <xuri.me@gmail.com>
Date: Thu, 4 Nov 2021 00:04:45 +0800
Subject: [PATCH] ref #65: new formula functions STANDARDIZE, STDEV.P and
 STDEVP

---
 calc.go      | 61 ++++++++++++++++++++++++++++++++++++++++++++++++++++
 calc_test.go | 20 +++++++++++++++++
 2 files changed, 81 insertions(+)

diff --git a/calc.go b/calc.go
index eac0f6c1..f4f6b0c4 100644
--- a/calc.go
+++ b/calc.go
@@ -542,9 +542,12 @@ type formulaFuncs struct {
 //    SMALL
 //    SQRT
 //    SQRTPI
+//    STANDARDIZE
 //    STDEV
+//    STDEV.P
 //    STDEV.S
 //    STDEVA
+//    STDEVP
 //    SUBSTITUTE
 //    SUM
 //    SUMIF
@@ -5994,6 +5997,64 @@ func (fn *formulaFuncs) SMALL(argsList *list.List) formulaArg {
 	return fn.kth("SMALL", argsList)
 }
 
+// STANDARDIZE function returns a normalized value of a distribution that is
+// characterized by a supplied mean and standard deviation. The syntax of the
+// function is:
+//
+//    STANDARDIZE(x,mean,standard_dev)
+//
+func (fn *formulaFuncs) STANDARDIZE(argsList *list.List) formulaArg {
+	if argsList.Len() != 3 {
+		return newErrorFormulaArg(formulaErrorVALUE, "STANDARDIZE requires 3 arguments")
+	}
+	x := argsList.Front().Value.(formulaArg).ToNumber()
+	if x.Type != ArgNumber {
+		return x
+	}
+	mean := argsList.Front().Next().Value.(formulaArg).ToNumber()
+	if mean.Type != ArgNumber {
+		return mean
+	}
+	stdDev := argsList.Back().Value.(formulaArg).ToNumber()
+	if stdDev.Type != ArgNumber {
+		return stdDev
+	}
+	if stdDev.Number <= 0 {
+		return newErrorFormulaArg(formulaErrorNA, formulaErrorNA)
+	}
+	return newNumberFormulaArg((x.Number - mean.Number) / stdDev.Number)
+}
+
+// stdevp is an implementation of the formula functions STDEVP and STDEV.P.
+func (fn *formulaFuncs) stdevp(name string, argsList *list.List) formulaArg {
+	if argsList.Len() < 1 {
+		return newErrorFormulaArg(formulaErrorVALUE, fmt.Sprintf("%s requires at least 1 argument", name))
+	}
+	varp := fn.VARP(argsList)
+	if varp.Type != ArgNumber {
+		return varp
+	}
+	return newNumberFormulaArg(math.Sqrt(varp.Number))
+}
+
+// STDEVP function calculates the standard deviation of a supplied set of
+// values. The syntax of the function is:
+//
+//    STDEVP(number1,[number2],...)
+//
+func (fn *formulaFuncs) STDEVP(argsList *list.List) formulaArg {
+	return fn.stdevp("STDEVP", argsList)
+}
+
+// STDEVdotP function calculates the standard deviation of a supplied set of
+// values.
+//
+//    STDEV.P( number1, [number2], ... )
+//
+func (fn *formulaFuncs) STDEVdotP(argsList *list.List) formulaArg {
+	return fn.stdevp("STDEV.P", argsList)
+}
+
 // TRIMMEAN function calculates the trimmed mean (or truncated mean) of a
 // supplied set of values. The syntax of the function is:
 //
diff --git a/calc_test.go b/calc_test.go
index b2fd5f4f..a2ac7199 100644
--- a/calc_test.go
+++ b/calc_test.go
@@ -911,6 +911,14 @@ func TestCalcCellValue(t *testing.T) {
 		"=SMALL(A1:B5,2)": "1",
 		"=SMALL(A1,1)":    "1",
 		"=SMALL(A1:F2,1)": "1",
+		// STANDARDIZE
+		"=STANDARDIZE( 5.5, 5, 2 )":   "0.25",
+		"=STANDARDIZE( 12, 15, 1.5 )": "-2",
+		"=STANDARDIZE( -2, 0, 5 )":    "-0.4",
+		// STDEVP
+		"=STDEVP(A1:B2,6,-1)": "2.40947204913349",
+		// STDEV.P
+		"=STDEV.P(A1:B2,6,-1)": "2.40947204913349",
 		// TRIMMEAN
 		"=TRIMMEAN(A1:B4,10%)": "2.5",
 		"=TRIMMEAN(A1:B4,70%)": "2.5",
@@ -2166,6 +2174,18 @@ func TestCalcCellValue(t *testing.T) {
 		"=SMALL(A1:A5,0)":    "k should be > 0",
 		"=SMALL(A1:A5,6)":    "k should be <= length of array",
 		"=SMALL(A1:A5,\"\")": "strconv.ParseFloat: parsing \"\": invalid syntax",
+		// STANDARDIZE
+		"=STANDARDIZE()":         "STANDARDIZE requires 3 arguments",
+		"=STANDARDIZE(\"\",0,5)": "strconv.ParseFloat: parsing \"\": invalid syntax",
+		"=STANDARDIZE(0,\"\",5)": "strconv.ParseFloat: parsing \"\": invalid syntax",
+		"=STANDARDIZE(0,0,\"\")": "strconv.ParseFloat: parsing \"\": invalid syntax",
+		"=STANDARDIZE(0,0,0)":    "#N/A",
+		// STDEVP
+		"=STDEVP()":     "STDEVP requires at least 1 argument",
+		"=STDEVP(\"\")": "#DIV/0!",
+		// STDEV.P
+		"=STDEV.P()":     "STDEV.P requires at least 1 argument",
+		"=STDEV.P(\"\")": "#DIV/0!",
 		// TRIMMEAN
 		"=TRIMMEAN()":        "TRIMMEAN requires 2 arguments",
 		"=TRIMMEAN(A1,\"\")": "strconv.ParseFloat: parsing \"\": invalid syntax",