Vectorization or Looping?

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Dave O 2022-11-27

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评论： Dave O 2022-11-27

I'm trying to accomplish a task through vectorization rather than reverting to my old habit of looping. I have a table, T, imported from a text file. The table is comprised of a list of items with a variable number of subtotals associated with each item. Is it possible to return the sum of the subtotals for each item without looping?

For example, with T below:

Var1 Var2

Item 1 NaN

Subtotal 1 1.4

Subtotal 2 0.7

Subtotal 3 5.4

Item2 NaN

Subtotal 1 1.9

Item 3 NaN

Subtotal 1 2.4

Subtotal 2 3.6

Desired output:

v1 v2

Item 1 7.5

Item 2 1.9

Item 3 6.0

v1 = find(contains(T.Var1,'Item'));

v2 = ?

Thanks in advance to anyone who can help!

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Stephen23 2022-11-27

编辑：Stephen23 2022-11-27

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The data arrangement make this challenging. A much better arrangement of the table data would be like this:

item = [1;1;1;2;3;3];
subt = [1.4;0.7;5.4;1.9;2.4;3.6];
tbl = table(item,subt)
tbl = 6×2 table
    item    subt
    ____    ____

     1      1.4 
     1      0.7 
     1      5.4 
     2      1.9 
     3      2.4 
     3      3.6 

Then your task is simple:

out = groupsummary(tbl,"item",@sum)
out = 3×3 table
    item    GroupCount    fun1_subt
    ____    __________    _________

     1          3            7.5   
     2          1            1.9   
     3          2              6   