MATLAB Answers

Append the tabelename to a variable name in a table

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alpedhuez on 14 Jun 2018
Commented: alpedhuez on 7 Jul 2018
I have a table T. There are variables a,b,... in T. I would like to rename variables so that their names will be T_a,T_b,...etc. Please advise.


alpedhuez on 14 Jun 2018
But then what will be a simple way to write the code for what you have said?
Stephen Cobeldick
Stephen Cobeldick on 14 Jun 2018
@alpedhuez: here is some pseudocode. Adjust to suit your situation:
S = dir(...)
T = readtable(S(1).name)
T.City = ... cityname: from filename ???
for k = 2:numel(S)
U = readtable(S(k).name)
U.City = ... cityname: from filename ???
T = [T;U]
This is untested, it is just to illustrate one way to import multiple tables so that you do not need to magically access the table names, and can simply include the city name as a column in the table.

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Answers (1)

Steven Lord
Steven Lord on 14 Jun 2018
Edited: Steven Lord on 14 Jun 2018
Have a variable in the combined table named City. Rows in the combined table that came from your New York table would have NY in that variable, and those that came from your San Francisco table would have SF in that variable. Once you've added that variable to each of your tables, join them together using City as your key variable.
Once you have that as a variable in your table you could use it as the grouping variable in calls to groupsummary if you want to compute, say, the total population for all the regions / boroughs / etc. in your table that are in NY.
mytable = table({'NY'; 'SF'; 'NY'; 'NY'; 'SF'}, [1; 2; 3; 4; 5], ...
'VariableNames', {'City', 'pop'})
totalPopulation = groupsummary(mytable, 'City', 'sum', 'pop')

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