Vlookup equivalent function for matlab

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!

Answer 1

[Jim Riggs]

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.

[Jim Riggs]

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.

[Jim Riggs]

No problem.

Just find the distance from each value to the value you wamt (i.e. subtract the target value from each data point) then take the absolute value of each, and find the minimum value. This is the one closest to the desired value.