Error in optimconstr() when used with single string vs array of string

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Ravi Raj Saxena
Ravi Raj Saxena 2023-3-30
评论： Aurele Turnes 2023-3-31
I'm working on MATLAB Version: 9.12.0.1884302 (R2022a) with Optimization Toolbox (9.3).
I have created 2 sets flight_name_set & Edges of type string
optimconstr gives the below error whenever the set is of single value but not on multiple values.
Error using optimconstr
Dimensions specifications must be a positive integer, string array, or a
cell array of character vectors.
For e.g
When Edges has 2 values Then there is no error.
flight_name_set =
1×5 string array
"Small-tt-1" "Medium-yy-2" "Medium-rr-3" "Jumbo-mm-4" "Jumbo-zz-5"
Edges =
1×2 string array
"W-Y" "S-Y"
optimconstr(Edges, flight_name_set, flight_name_set)
ans =
2×5×5 OptimizationConstraint array with properties:
IndexNames: {{1×2 cell} {1×5 cell} {1×5 cell}}
Variables: [1×1 struct] containing 0 OptimizationVariables
See constraint formulation with show.
but when Edges have 1 value there is error
flight_name_set =
1×5 string array
"Small-tt-1" "Medium-yy-2" "Medium-rr-3" "Jumbo-mm-4" "Jumbo-zz-5"
Edges =
"W-Y"
optimconstr(Edges, flight_name_set, flight_name_set)
Error using optimconstr
Dimensions specifications must be a positive integer, string array, or a cell array of character vectors.
With hit and trial I have to put a check on length and then use {Edges{:}} if there is only 1 value. Is there a way to use genralise statements?

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采纳的回答

Raghunathraju
Raghunathraju 2023-3-31
Hi Raviraj,
The 'optimconstr' function cannot have a single argument as string, The input arguments can be a string array, a cell array, or it can be a positive integer .If you want to use a string as an input argument then it must be an array of strings.
  2 个评论
Aurele Turnes
Aurele Turnes 2023-3-31
When you have a single element, you should use a cell array of character vectors like this:
optimconstr(cellstr(Edges), flight_name_set, flight_name_set)
This is because optimconstr and optimexpr go hand-in-hand with optimvar, which accepts string inputs and name-value arguments. For this reason, when writing:
optimvar("x", "Typo", "integer")
It is impossible to know if this is a typo and means:
optimvar("x", "Type", "integer")
or if this means:
optimvar("x", {'Typo'}, {'integer'})
To avoid silently returning the wrong answer, we error and require to pass a cell array for a single string input. Optimexpr and optimconstr behave similarly for consistency.

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