Look up tables Flashcards
1
Q
What are the characteristics of LUT? (6)
A
- increases complexity
- list of discrete pairs = described by identifier + output
- array = discrete points where each point = describes as pair - (x y)
- each x-variable defined = LUT = corresponding y-variable
- may = used to approx./predefined functions
- VENSIM interpolates discrete points in LUT
2
Q
What are the advantages of LUT? (5)
A
- allows VENSIM = avoid computing complex mathematical calculations
- predefining a function = improves processing speed
- faster to access output from list than computing a calculation
- require input = to access discrete points in LUT
- LUT = stored in memory
3
Q
What are the disadvantages of LUT? (2)
A
- memory usage = data points stored in LUT’s
- LUT’s take up space in memory = some values ≠ used = waste space
4
Q
Example of a LUT:
A
5
Q
Graph for y = f(x) = 3
A
6
Q
Insulin production rate lookup table:
b = 1
insulin production rate = beta x glucose concentration
A
7
Q
What are the assumptions for the insulin production rate? (3)
A
- assume beta = constant
- assume glucose concentration = a variable
- based on LRD: insulin production rate = beta x glucose concentration
8
Q
2 Editor Options
graphical LU editor =
equation editor =
A
view graph
put pairs in table
9
Q
glucose concentration (___-axis) insulin production rate (__-axis)
A
x
y
10
Q
f(x) =
A
insulin production rate = beta (glucose concentration)
11
Q
What does the Graphical loop-up editor allow? (3)
A
- allows = click on graph points = add points in LUT
- allows adjustment of points = move on graph
- allows = find what = x vs. y
12
Q
Practically, insulin production = _____
insulin production rate = ___-shaped response to glucose concentration
A
non-linear
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