====== Four-point function ======

{{:en:mervis-ide:35-help:b81.png}}

===== Block name =====

B81_FOURPOINTFUNCTIONNODE

===== ST call =====

<code st-iec>
PROGRAM TEST2_B80
 VAR
 FB:LIB.CORE.V1_0.B81_FOURPOINTFUNCTIONNODE;
 IN_V:REAL;
 X1_V:REAL:=0;
 X2_V:REAL:=20;
 X3_V:REAL:=60;
 X4_V:REAL:=80;
 Y1_V:REAL:=0;
 Y2_V:REAL:=100;
 Y3_V:REAL:=150;
 Y4_V:REAL:=180;
 OUT_V:REAL;
 END_VAR 
FB(IN:=IN_V, X1:=X1_V, X2:=X2_V, X3:=X3_V, X4:=X4_V, Y1:=Y1_V, Y2:=Y2_V, Y3:=Y3_V, Y4:=Y4_V);
OUT_V:=FB.OUT;
END_PROGRAM
</code>

===== Library =====

LIB\CORE

===== Version =====

V1.0

===== Description =====

Block defines an arbitrary transfer curve given by four points.\\


===== Inputs =====

|Input|Type|Description          |Default value|
|IN   |REAL|Input signal         |0            |
|X1   |REAL|1.point, x coordinate|0            |
|X2   |REAL|2.point, x coordinate|1            |
|X3   |REAL|3.point, x coordinate|2            |
|X4   |REAL|4.point, x coordinate|3            |
|Y1   |REAL|1.point, y coordinate|0            |
|Y2   |REAL|2.point, y coordinate|1            |
|Y3   |REAL|3.point, y coordinate|2            |
|Y4   |REAL|4.point, y coordinate|3            |

===== Outputs =====

|Output|Type|Description              |
|OUT   |REAL|Output signal            |
|SIGN  |BOOL|Sign of the output signal|

===== Function =====

The block implements an arbitrary transfer curve given by four points – //[X1,Y1],// //[X2,Y2],[X3,Y3],[X4,Y4]//. The function is constant behind the last point and before the first point as well, see the Figure below.\\
\\
{{:en:mervis-ide:35-help:b81_2.png}}

===== Application example =====

Let us create a function which is depicted on the Figure below, right. According to the Figure we want an increasing function with slope //1// for "all possible values" greater then zero. If "all possible values" in our case are less then for example //1000// we can solve the problem by the following setting: //[X1,Y1]=[0,0], [X2,Y2]=[X3,Y3]=[X4,Y4]=[1000,1000].\\
// {{:en:mervis-ide:35-help:b81_3.png}}\\
\\