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Vlookup equivalent function for matlab

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Jung
Jung on 16 Dec 2019
Commented: Jim Riggs on 17 Dec 2019
Hello,
I have two tables (table 1: 241x2 and table 2: 241x35).
I would like to use something similar to vlookup to find the subbasin area that matches the subbasin #. I have 241 subbasins.
Would appreciate your help!

Accepted Answer

Jim Riggs
Jim Riggs on 16 Dec 2019
Edited: Jim Riggs on 17 Dec 2019
If your data is in a 2D table (matrix) and you want to locate a column that matches the exact value from another column, then logical indexing is a natural way to go.
Suppose data(:,1) represents the column of subbasin number, and data(:,2) represents the column of area, then to select an area for a given subbasin number
subbasin_no = 12;
area = data((data(:,1)==subbasin_no),2);
"area" contains every value from column 2 where column 1 = subbasin_no.
Note that this is more versatile than VLOOKUP in Excel.
1) The data does not have to be monotonically increasing, as with VLOOKUP
2) You can use logical indexing based on any column (with VLOOKUP, you must perform the look-up based on column 1)
3) It can return multiple values.
  1 Comment
Jim Riggs
Jim Riggs on 17 Dec 2019
You can make this into a function similar to Vlookup in Excel. For example:
Vlookup = @(data,col1,val1,col2) data((data(:,col1)==val1),col2);
The function Vlookup takes 4 arguments;
  1. data is the table of data
  2. col1 is the column you want to use to perform the lokup
  3. val1 is the value you want to look up (from col1).
  4. col2 is the column that you want to retrieve.
So, in my previous example, this would be
area = Vlookup(data, 1, 12, 2);
Look up from the "data" table, where column 1 has a value of 12, and return the value from column 2.

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