Hi all, I want to write a code that assign new column to the table. For example, I have a column like:

Land Cover             Soil Group         Value
Forest            A
Urban             B
Vegetation        C

I want to create new column called "Value". This "Value" depends on Land Cover and Soil Group. For example If Land Cover is Forest and Soil Group is B, Value should be 50. Or If Land Cover is Urban and Soil Group is C, Value should be 75. How can I write it ? Thank you for your help

Answer 1

[Peter Perkins]

Part of this question has nothing to do with tables, the other part does:

1) Not sure how 50 comes from Forest,B, but let's assume you have a desired value for every possibility in the 3x3 set of combinations. You can make a matrix, and use sub2ind to get the right elements for each actual combination.

2) If your table is called t, and your function is called fun, a simple assignment using dot subscripting will create a new variable.

Consider using a table, and categorical variables for LandCover and SoilType. Put all that together, and it looks like this:

>> LandCover = categorical([1;2;3;1;2;3],1:3,{'Forest' 'Urban' 'Vegetation'});
>> SoilType = categorical([1;1;2;2;3;3],1:3,{'A' 'B' 'C'});
>> t = table(LandCover,SoilType)
t =
  6×2 table
    LandCover     SoilType
    __________    ________
    Forest           A    
    Urban            A    
    Vegetation       B    
    Forest           B    
    Urban            C    
    Vegetation       C    

>> t.Value = fun(t.LandCover,t.SoilType)
t =
  6×3 table
    LandCover     SoilType    Value
    __________    ________    _____
    Forest           A          1  
    Urban            A          4  
    Vegetation       B          8  
    Forest           B         50  
    Urban            C         75  
    Vegetation       C          9

with

function v = fun(lc,st)
values = [1 50 3; 4 5 75; 7 8 9];
i = sub2ind([3 3],double(lc),double(st));
v = values(i);