DIFF returns the derivative in a location in a two- or more dimensional space

Syntax

1. DIFF(Pno%, Ndim%, "ColLab$_1,.., "ColLab$_Ndim%", Xint_1, ..., Xint_Ndim%-1, [DirivNo%])
2. DIFF(0, Npoints%, x_1, y_1, x_2, y_2,…, x_n, y_n, Xint, [DirivNo%=1]) (only in 2D)
3. DIFF(@ObjFn(..), Ndim%, @ObjColPar_1,.., @ObjColPar_Ndim%, Xint_1, ..., Xint_Ndim%-1, [DirivNo%])
4. DIFF(Telitab$, Ndim%, "ColLab$_1",.., "ColLab$_Ndim%", Xint_1, ..., Xint_Ndim%-1, [DirivNo%])

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1. See also Telitab access for a generic description on the use of TeLiTab data
2. Similar to other Data analysis functions, the DIFF is a convenient way to evaluate data. Please also look at these functions for syntax examples
3. Please realise the dataset provided to DIFF should be a function. Every x-value should have one y-value. Furthermore, in case of a multi-dimensional dataset you should provide a matrix of coordinates.
4. Extrapolation outside the x-range is performed parabolically.

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In this example, the TeLiTab is addressed in the Dataslot. The function y is defined as y = DIFF(1, 2, "XC", "YC", x, 1) With the following Telitab set in the Data slot:

|DIFF1DIFF1|
0
2
"XC" "YC"
"1" 1 1
"2" 2 4
"3" 3 9
"4" 4 16
"5" 5 25
"6" 6 36
"7" 7 49
"8" 8 64
"9" 9 81
"10" 10 100|

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In direct definition, the points of the curve are stated in the Relation itself. This method can only be used for 2D derivatives, the syntax is: DIFF(Pno%, Ndim%, "ColLab$_1,.., "ColLab$_Ndim%", Xint, [DirivNo%]) If Pno%=0 then all x_i and y_i values should be numeric expressions. The minimum number of x,y data points Ndim% in the list is 2 in which case the interpolation (and differentiation) is performed linear. Let the function y be defined as

y = DIFF(0, 4, 1, 1, 2, 4, 3, 9, 4, 16, x, 1) For x=2.5, this function returns

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And use the following relation to determine the derivative:

Calculated_Value=DIFF(DataSet2#,3,"X","Y","Z", Input_Value_x, Input_Value_y, OptionalDirivNo) 

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