Generate Field Names from Variables While Accessing Elements of a Nonscalar Structure Array
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I have a top-level 1x20 structure arrray with 10 fields which is generated using code similar to below with no problems (this is an extract of a larger script).
for nLap = 1:R2(nDriver).Laps
R2(nDriver).LapData(nLap).LapTime = sessions.R2.Sectors.(nDriverStr).LapTime(nLap);
R2(nDriver).LapData(nLap).SectoR2 = sessions.R2.Sectors.(nDriverStr).S1Time(nLap);
R2(nDriver).LapData(nLap).Sector2 = sessions.R2.Sectors.(nDriverStr).S2Time(nLap);
R2(nDriver).LapData(nLap).Sector3 = sessions.R2.Sectors.(nDriverStr).S3Time(nLap);
R2(nDriver).LapData(nLap).TIS = sessions.R2.Sectors.(nDriverStr).TiS(nLap);
end
However, I need to run this for many other structures by replacing the 'R2' to 'R1' for example.
Previously, I have done that in the same way that the (nDriverStr) variable in used to enter a field within the structure, however this does not seem to work when I am already referencing a row within the structure such as:
(R)(nDriver).LapData(nLap).LapTime = sessions.(R).Sectors.(nDriverStr).LapTime(nLap);
Is there a way to do this using R as a variable string which loops through "R1", "R2", "R3" for example?
4 件のコメント
Stephen23
2022 年 6 月 30 日
編集済み: Stephen23
2022 年 6 月 30 日
"What about the naming here makes these badly named?"
Forcing pseudo-indices into variable names mixes (meta-)data into your code, with the end result of forcing yourself into writing slow, complex, inefficient, insecure code when trying to access that data:
Using pseudo-indices in fieldnames or variable names (e.g. "R1", "R2", etc) is almost always better replaced with actual indices into one array. When you see yourself adding numbers onto field/variable names, you must ask yourself if those are pseudo-indices (slow and complex) that should be actual indices (simple and very efficient).
" Structures are new to me but when I found them, they seemed to be the most natural way of storing this data."
In my opinion, structures are a great way to store imported data, because they make it easy to store the improted data together with any assocaited meta-data (e.g. filenames, test information, etc). But rather than nesting more structures by dynamic fieldnames using some meta-data, it is often better to use a structure array and fixed fieldnames, e.g.:
S(1).data = ..
S(1).name = ..
S(1).test = ..
S(2).data = ..
S(2).name = ..
S(2).test = ..
etc.
This makes looping over them simpler and very efficient, and it also means that you can use comma-separated lists:
"... am currently experimenting with an alternative way of storing them."
Keep experimenting!
Steven Lord
2022 年 6 月 30 日
What about the naming here makes these badly named?
name = 'why, x'; % Specified by user or written as a file name?
eval([name '.foo = 1'])
Now picture a system or quit call in place of the why call.
回答 (1 件)
Matt J
2022 年 6 月 30 日
Why not a 2D struct array,
R(nDriver,1).LapData(nLap).LapTime
R(nDriver,2).LapData(nLap).LapTime
R(nDriver,3).LapData(nLap).LapTime
0 件のコメント
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