Difference between revisions of "Array-reducing functions"

Revision as of 03:20, 11 December 2015

Analytica User GuideMore Array FunctionsArray-reducing functions

An array-reducing function operates across a dimension of an array and returns a result that has one dimension less than the number of dimensions of its input array. When applied to an array of n dimensions, a reducing function produces an array that contains n-1 dimensions. Examples include, Sum(x, i), Product(x,i), Max(x, i), Min(x, i), and others described below. The subscript construct x[i = v] and related subscript and slice functions also reduce arrays by a dimension (see Subscript and slice of a subarray).

The function Sum(x, i) illustrates some properties of reducing functions.

Examples

Sum(Car_prices, Car_type) →

Years ▶
2005	2006	2007	2008	2009
59K	62K	66K	71K	76K

Sum(Car_prices, Years) →

Car_type ▶
VW	Honda	BMW
99K	103K	141K

Sum(Sum(Car_prices, Years), Car_type) → 334K

See Array Function Example Variables for example array variables used here and below.

Tip

The second parameter, i, specifying the dimension over which to sum, is optional. But if the array, x, has more than one dimension, Analytica might not sum over the dimension you expect. For this reason, it is safer always to specify the dimension index explicitly in Sum() or any other array-reducing function.

@@ Line 4: / Line 4: @@
 __TOC__
-An array-reducing function operates across a dimension of an array and returns a result that has one dimension less than the number of dimensions of its input array. When applied to an array of <code>n</code> dimensions, a reducing function produces an array that contains <code>n-1</code> dimensions. Examples include, '''Sum(x, i)''', Product(x,i), Max(x, i), Min(x, i)''', and others described below. The subscript construct '''x[i = v]''' and related subscript and slice functions also reduce arrays by a dimension (see [[Subscript and slice of a subarray]]).
+An array-reducing function operates across a dimension of an array and returns a result that has one dimension less than the number of dimensions of its input array. When applied to an array of <code>n</code> dimensions, a reducing function produces an array that contains <code>n-1</code> dimensions. Examples include, '''Sum(x, i), Product(x,i), Max(x, i), Min(x, i)''', and others described below. The subscript construct '''x[i = v]''' and related subscript and slice functions also reduce arrays by a dimension (see [[Subscript and slice of a subarray]]).
 The function '''Sum(x, i)''' illustrates some properties of reducing functions.
@@ Line 12: / Line 12: @@
 <code>Sum(Car_prices, Car_type) →</code>
-<code>Variable Rate_of_inflation :=</code>
 {| class=''wikitable'' border="1"
-! colspan="5" style="text-align: left;" | Years &#9654;
+! colspan="5" | Years &#9654;
 |-
 ! style="width:75px;" |'''2005            '''
@@ Line 28: / Line 27: @@
 | 76K
 |}
+<code>Sum(Car_prices, Years) →</code>
+{| class=''wikitable'' border="1"
+! colspan="3" | Car_type &#9654;
+|-
+! style="width:75px;" |'''VW            '''
+! style="width:75px;" |'''Honda           '''
+! style="width:75px;" |'''BMW           '''
+|-
+| 99K
+| 103K
+| 141K
+|}
+<code>Sum(Sum(Car_prices, Years), Car_type) → 334K</code>
+See [[Array Function Example Variables]] for example array variables used here and below.
+<tip title="Tip">The second parameter, '''i''', specifying the dimension over which to sum, is optional. But if the array, '''x''', has more than one dimension, Analytica might not sum over the dimension you expect. For this reason, it is safer always to specify the dimension index explicitly in '''Sum()''' or any other array-reducing function.</Tip>
 ==See Also==
 <footer>Functions that create arrays / {{PAGENAME}} / Transforming functions</footer>