DQUAD returns a double quadratic interpolated value in two or more dimensions

Syntax

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

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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 DQUAD function provides a convenient way to manipulate curve data, either available in the knowledge base or produced by satellites. The routine contains a double quadratic interpolator. Extrapolation outside the x-range is performed parabolic.
3. Please realise the dataset provided to DQUAD should be a function. Every x-value should have one y-value. When you do not have a valid dataset, please look at GAUSSINT() or LEASQ()

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The function y is defined as

y = DQUAD(1, 2, "XC", "YC", x, 1)

With the following Telitab set in the Data slot:

|DQUAD1|
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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The expression is the following:

R_TOT=DQUAD(1, 3, "DRAFT", "VS", "R-TOT", Draft, Vs)

And the dataslot containing:

|DQUAD1|
0
3 "DRAFT" "VS" "R-TOT"
"1" 5 10 10000
"2" 5 11 11000
"3" 5 12 12000
"4" 6 10 11000
"5" 6 11 12000
"6" 6 12 13000
"7" 7 10 12000
"8" 7 11 13000
"9" 7 12 14000|

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In direct definition, the points needed for interpolation are stated in the Relation itself. This method can only be used for 2D interpolation. The syntax is

DQUAD( Pno%, Npoints%, x_1, y_1, x_2, y_2,…, x_n, y_n, Xint, [DirivNo%=1])

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