DQUAD returns a double quadratic interpolated value in two or more dimensions
Arguments
The function y is defined as
y = DQUAD(1, 2, "XC", "YC", x, 1)
With the following Telitab set in the Data slot:
|DQUAD1DQUAD1|
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|
For x = 2.5, this relation returns
y=6.25
NOTE: In case you apply the symbolic addressing of the columns for the description of the point on the curve or surface to compute the differential for, e.g. "Par_x" and "Par_y", please make sure that your Telitab set contains these names. If not, an error message is generated and the calculation is stopped.
...
The expression is the following:
R_TOT=DQUAD(1, 3, "DRAFT", "VS", "R-TOT", Draft, Vs)
And the dataslot containing:
|DQUAD1DQUAD1|
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|
For Draft=5.6 m and Vs=11.8 m/s, the function returns
R R-TOT=12400 N
The matrix interpolation can be applied in all except Method 2, obviously not in Method 2 since only x,y data points are provided in that case.
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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])
If Pno%=0 then all x_i and y_i values should be numeric expressions. The minimum number of x,y data points Npoints% in the list is 2 in which case the interpolation (and differentiation) is performed linear. Let y be a function defined by
y = DIFF DIFF(0, 4, 1, 1, 2, 4, 3, 9, 4, 16, x, 1)
For x=2.5, this equation returns
y=6.25
These methods are similar to syntax 1, for information on how to acces the TeLiTab data with those methods see: TeLiTab access.
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