Difference between revisions of "If Command"

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<noinclude>{{Manual Page|version=4.0}}[[Category:Manual (official)|{{PAGENAME}}]]</noinclude>
 
<noinclude>{{Manual Page|version=4.0}}[[Category:Manual (official)|{{PAGENAME}}]]</noinclude>
 
{{command|logical}}
 
{{command|logical}}
; If[Condition, Object]: Yields a copy of the object if the condition evaluates to ''true'', and an undefined object if it evaluates to ''false''.
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; If[ <Condition>, <Object> ]: Yields a copy of the object if the condition evaluates to ''true'', and an undefined object if it evaluates to ''false''.
; If[Condition, Object a, Object b]: Yields a copy of object ''a'' if the condition evaluates to ''true'', and a copy of object ''b'' if it evaluates to ''false''.
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; If[ <Condition>, <Object a>, <Object b> ]: Yields a copy of object ''a'' if the condition evaluates to ''true'', and a copy of object ''b'' if it evaluates to ''false''.
 
{{warning|Both objects must be of the same type.}}
 
{{warning|Both objects must be of the same type.}}
  
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The ''If'' command can be used to create conditional functions. Such conditional functions may be used as arguments in any command that takes a function argument, such as [[Derivative Command|Derivative]], [[Integral Command|Integral]], and [[Intersect Command|Intersect]].
 
The ''If'' command can be used to create conditional functions. Such conditional functions may be used as arguments in any command that takes a function argument, such as [[Derivative Command|Derivative]], [[Integral Command|Integral]], and [[Intersect Command|Intersect]].
  
{{Example|1=<div>  
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{{Examples|1=<div>  
 
* <code>f(x) = If[x < 3, sin(x), x^2]</code> yields a function that equals ''sin(x)'' for ''x < 3'' and ''x<sup>2</sup>'' for ''x ≥ 3''
 
* <code>f(x) = If[x < 3, sin(x), x^2]</code> yields a function that equals ''sin(x)'' for ''x < 3'' and ''x<sup>2</sup>'' for ''x ≥ 3''
 
* <code>f(x) = If[x < 3 ∧ x>0, x^3]</code> yields a function that equals ''sin(x)'' for x between 0 and 3 and undefined for ''x ≥ 3'' or ''x ≤ 0''.</div>}}
 
* <code>f(x) = If[x < 3 ∧ x>0, x^3]</code> yields a function that equals ''sin(x)'' for x between 0 and 3 and undefined for ''x ≥ 3'' or ''x ≤ 0''.</div>}}

Revision as of 17:09, 7 November 2012


If[ <Condition>, <Object> ]
Yields a copy of the object if the condition evaluates to true, and an undefined object if it evaluates to false.
If[ <Condition>, <Object a>, <Object b> ]
Yields a copy of object a if the condition evaluates to true, and a copy of object b if it evaluates to false.
Warning Warning: Both objects must be of the same type.

Conditional Functions

The If command can be used to create conditional functions. Such conditional functions may be used as arguments in any command that takes a function argument, such as Derivative, Integral, and Intersect.

Examples:
  • f(x) = If[x < 3, sin(x), x^2] yields a function that equals sin(x) for x < 3 and x2 for x ≥ 3
  • f(x) = If[x < 3 ∧ x>0, x^3] yields a function that equals sin(x) for x between 0 and 3 and undefined for x ≥ 3 or x ≤ 0.
Note: See section: Boolean values for the symbols used in conditional statements.
Note: Derivative of If[condition, f(x), g(x)] gives If[condition, f'(x), g'(x)]. It does not do any evaluation of limits at the critical points.

If Command in Scripting

In many programming languages if has the meaning "If condition holds, do something; otherwise do something else". In GeoGebra, arguments of If are not commands, but values, one of which becomes the value of the result. Therefore if you want to e.g. set value of b to 3 provided a > 2, correct way to do this is SetValue[b,If[a>2,3,b]]. The other way of nesting SetValue and If is incorrect.

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