Difference between revisions of "KeepIf Command"

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<noinclude>{{Manual Page|version=4.0}}[[Category:Manual (official)|{{PAGENAME}}]]</noinclude>
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<noinclude>{{Manual Page|version=5.0}}</noinclude>{{command|logical}}
{{command|logical}}
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; KeepIf( <Condition>, &lt;List> ): Creates a new list that only contains those elements of the initial list that fulfil the condition.
; KeepIf[ <Condition>, <List> ]: Creates a new list that only contains those elements of the initial list that fulfil the condition.
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: {{Example|1=<code>KeepIf(x<3, {1, 2, 3, 4, 1, 5, 6})</code> returns the new list ''{1, 2, 1}''.}}
: {{Example|1=<code>KeepIf[x<3, {1, 2, 3, 4, 1, 5, 6}]</code> returns the new list ''{1, 2, 1}''.}}
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:{{note|1=For list of numbers arbitrary condition may be used. For list of other objects one can use only conditions of the form <code>x==constant</code> or <code>x!=constant</code>.}}
{{note|1=For list of numbers arbitrary condition may be used. For list of other objects one can use only conditions of the form <code>x==constant</code> or <code>x!=constant</code>.}}
 
  
 
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; KeepIf( <Condition>, <Variable>, &lt;List> )
{{betamanual|version=4.2|
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: This syntax allows a more flexible condition.
1=; KeepIf[ <Condition>, <Variable>, <List> ]
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: {{Example|1=For Points ''P, Q, R'' <code>KeepIf(x(A) < 3, A, {P, Q, R})</code> will filter the points whose ''x''-coordinate is less than ''3'' out of the list. The variable ''A'' is replaced in turn with ''P'' then ''Q'' then ''R'' for the check.}}
: This syntax allows a more flexible condition, eg for Points P, Q, R <code>KeepIf[x(A) < 3, A, {P, Q, R}]</code> will filter the points whose ''x''-coordinate is greater than 3 out of the list. The Variable A is replaced in turn with ''P'' then ''Q'' then ''R'' for the check.
 
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Latest revision as of 19:43, 30 September 2017


KeepIf( <Condition>, <List> )
Creates a new list that only contains those elements of the initial list that fulfil the condition.
Example: KeepIf(x<3, {1, 2, 3, 4, 1, 5, 6}) returns the new list {1, 2, 1}.
Note: For list of numbers arbitrary condition may be used. For list of other objects one can use only conditions of the form x==constant or x!=constant.
KeepIf( <Condition>, <Variable>, <List> )
This syntax allows a more flexible condition.
Example: For Points P, Q, R KeepIf(x(A) < 3, A, {P, Q, R}) will filter the points whose x-coordinate is less than 3 out of the list. The variable A is replaced in turn with P then Q then R for the check.
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