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How to call/create column variables from changeable table?

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Ana Castanheiro
Ana Castanheiro 2018-1-29
评论： Peter Perkins 2020-4-15
Hi! I have this table (see image) from which I need to call all individual columns using their column names. For example, for using a variable called Fe to retrieve the Fe column, and so on for all columns. I know I can do this by using tablename.Fe, but I'm looking for a more efficient and automatic way, because:
  1. there are dozens of columns to be retrieved
  2. the order/size of the initial data table differs from sample to sample (especially because of this!)
In the end, I want to be able to use these variables for further operations, for example to do cluster analysis by focusing on specific elements only (e.g. data1 = [S Al Si Ca Fe];).
Any help is really appreciated!

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Peter Perkins
Peter Perkins 2018-1-30
编辑：Peter Perkins 2018-1-31
I think what you are looking for is either
data1 = data(:,{'S' 'Al' 'Si' 'Ca' 'Fe'})
or
data1 = data{:,{'S' 'Al' 'Si' 'Ca' 'Fe'}}
depending on whether you want a subtable or a numeric matrix. And of course you could substitute [10 7 8 13 17] for those names in either case. There's a whole section in the doc about table subscripting.
  2 个评论
Jörg Ho
Jörg Ho 2020-3-31
Hi,
I have a similar problem, but the solution won't fit. 'data1' is a table as well as 'data'. What I want is to create a number of arrays (in this example would it be for the names of the arrays: data.Properties.VariableNames) with its data from the table.
I thought of a loop over the names like:
for item=data.Properties.VariableNames
? = table2array(data(:,item))
end
But, how do I get the value of 'item' in place of the '?'?
Thanks a lot,
Jörg Ho
Peter Perkins
Peter Perkins 2020-4-15
Very likely you do not want to do that. Unless you have a very small number of variables in your table, you will end up with many things in your workspace, and no good way to address them. If you do have only a very small number of variables in the table, do it by hand.
You have those data in a table. You can refer to them by name using dot subscripting, for example
data.ItemName
and you can easily loop over them, referring to each one as
data.(data.Properties.VariableNames{i})
or even
data.(i)
" 'data1' is a table as well as 'data'."
No, it isn't if you use braces, not parentheses. More information in the doc section I referred to.

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