How to place values in a matrix with values from another matrix?

I have 2 tables A and B:

      A                 B 
2018     13         2018    0.2
2019     15         2019    0.3    
2020    -76         2020    0.4
2021    -1          2020    0.6
2022     0          2020    0.1
                    2021    0.7
                    2021    0.1

I want to expand B by adding an additional column from A which is related to the first column of both tables: wherever the year (=column 1) is the same, the value from A(:,2) should be added in a 3rd column in B.

The new table B should thus look as follows:

      A                      B 
2018     13         2018    0.2      13
2019     15         2019    0.3      15   
2020    -76         2020    0.4     -76
2021    -1          2020    0.6     -76
2022     0          2020    0.1     -76
                    2021    0.7     -1
                    2021    0.1     -1

Thank you in advance!

Answer 1

[Arif Hoq]

Year=[2018;2019;2020;2021;2022];
value1=[13;15;-76;-1;0];
table1=table2array(table(Year,value1))

table1 = 5×2

2018 13 2019 15 2020 -76 2021 -1 2022 0

Year2=[2018;2019;2020;2020;2020;2021;2021;];
value2=[0.2;0.3;0.4;0.6;0.1;0.7;0.1;];
table2=table2array(table(Year2,value2))

table2 = 7×2

1.0e+03 * 2.0180 0.0002 2.0190 0.0003 2.0200 0.0004 2.0200 0.0006 2.0200 0.0001 2.0210 0.0007 2.0210 0.0001

[idx out]=ismember(table2(:,1),table1(:,1));
newcol=table1(out,2);
newtable=table(Year2,value2,newcol)

newtable = 7×3 table
    Year2    value2    newcol
    _____    ______    ______

    2018      0.2        13  
    2019      0.3        15  
    2020      0.4       -76  
    2020      0.6       -76  
    2020      0.1       -76  
    2021      0.7        -1  
    2021      0.1        -1  

Answer 2

[Peter Perkins]

This is a one-liner with join. You have time, so use a timetable:

>> year = datetime([2018;2019;2020;2021;2022],1,1); x = [13;15;-76;-1;0];
A = timetable(year,x)
A =
  5×1 timetable
       year         x 
    ___________    ___
    01-Jan-2018     13
    01-Jan-2019     15
    01-Jan-2020    -76
    01-Jan-2021     -1
    01-Jan-2022      0
>> year = datetime([2018;2019;2020;2020;2020;2021;2021],1,1); y = [.2;.3;.4;.6;.1;.7;.1];
B = timetable(year,y)
B =
  7×1 timetable
       year         y 
    ___________    ___
    01-Jan-2018    0.2
    01-Jan-2019    0.3
    01-Jan-2020    0.4
    01-Jan-2020    0.6
    01-Jan-2020    0.1
    01-Jan-2021    0.7
    01-Jan-2021    0.1
>> B = join(B,A,"Keys","year")
B =
  7×2 timetable
       year         y      x 
    ___________    ___    ___
    01-Jan-2018    0.2     13
    01-Jan-2019    0.3     15
    01-Jan-2020    0.4    -76
    01-Jan-2020    0.6    -76
    01-Jan-2020    0.1    -76
    01-Jan-2021    0.7     -1
    01-Jan-2021    0.1     -1