Difference between revisions of "If Command"

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===Conditional Functions===
 
===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 Command|Derivative]], [[Integral Command|Integral]], and [[Intersect Command|Intersect]].
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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]].
 
:{{Examples|1=<div>  
 
:{{Examples|1=<div>  
 
:* <code>f(x) = If[x < 3, sin(x), x^2]</code> yields a piecewise 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 piecewise function that equals ''sin(x)'' for ''x < 3'' and ''x<sup>2</sup>'' for ''x ≥ 3''.
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==If Command in Scripting==
 
==If Command in Scripting==
:If command can be used in scripts to perform different actions under certain conditions.
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:'''If''' command can be used in scripts to perform different actions under certain conditions.
 
:{{example|1= Let ''n'' be a number, and ''A'' a point. The command <code>If[Mod[n, 7] == 0, SetCoords[A, n, 0], SetCoords[A, n, 1]]</code> modifies the coordinates of point ''A'' according to the given condition. In this case it would be easier to use  <code> SetCoords[A, n, If[Mod[n, 7] == 0,0,1]]</code>.
 
:{{example|1= Let ''n'' be a number, and ''A'' a point. The command <code>If[Mod[n, 7] == 0, SetCoords[A, n, 0], SetCoords[A, n, 1]]</code> modifies the coordinates of point ''A'' according to the given condition. In this case it would be easier to use  <code> SetCoords[A, n, If[Mod[n, 7] == 0,0,1]]</code>.
 
}}
 
}}
:{{note|1= Arguments of If must be Objects or [[Scripting Commands]], not assignments. Syntax <code><nowiki>b = If[a > 1, 2, 3]</nowiki></code> is correct, but ''b = 2'' or ''b = 3'' would not be accepted as parameters of If.}}
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:{{note|1= Arguments of '''If''' must be Objects or [[Scripting Commands]], not assignments. Syntax <code><nowiki>b = If[a > 1, 2, 3]</nowiki></code> is correct, but ''b = 2'' or ''b = 3'' would not be accepted as parameters of If.}}

Revision as of 14:13, 16 July 2013



If[ <Condition>, <Then> ]
Yields a copy of the object Then if the condition evaluates to true, and an undefined object if it evaluates to false.
Example:
If[true, x + y = 4] yields line x + y = 4
If[ <Condition>, <Then>, <Else> ]
Yields a copy of object Then if the condition evaluates to true, and a copy of object Else if it evaluates to false.
Warning Warning: Both objects must be of the same type.
Example:
  • If[true, x + y = 4, x - y = 4] yields line x + y = 4
  • If[false, x + y = 4, x - y = 4] yields line x - y = 4


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 piecewise function that equals sin(x) for x < 3 and x2 for x ≥ 3.
  • f(x) = If[0 <= x <= 3, sin(x)] yields a function that equals sin(x) for x between 0 and 3 (and undefined otherwise).
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.
Note: See section: Boolean values for the symbols used in conditional statements.


If Command in Scripting

If command can be used in scripts to perform different actions under certain conditions.
Example: Let n be a number, and A a point. The command If[Mod[n, 7] == 0, SetCoords[A, n, 0], SetCoords[A, n, 1]] modifies the coordinates of point A according to the given condition. In this case it would be easier to use SetCoords[A, n, If[Mod[n, 7] == 0,0,1]].
Note: Arguments of If must be Objects or Scripting Commands, not assignments. Syntax b = If[a > 1, 2, 3] is correct, but b = 2 or b = 3 would not be accepted as parameters of If.
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