How to merge two tables into a single table?

Hi all!

I may ask for a simple task, but im stuck at this point.

So, let's imagine I have two tables randomnly generated as follow:

table1 = table(["Smith";"Nguyen";"Williams";"Fernandez";"Brown"],[38;43;38;40;49], ...
          [71;69;64;67;64],[176;163;131;133;119]) % Randomly generated table1
table1.Properties.VariableNames = ["LastName","Age","Height","Weight"] % Adding headers


table2 = table(["James";"Mary";"Anna";"Jhon";"Pow"],[67;49;18;95;29;67;36], ...
          [31;65;23;17;48];90,[16;63;13;33;1;765]) % Randomly generated table2
table2.Properties.VariableNames = ["LastName","Age","Height","Weight"] % Adding headers

I'd like to merge table1 and tabl 2 into one single table (let's call it table3), but indicating in the table3 header row the original table from which the data belong (this is, maybe specifying table1 and table2 across one single column, as a variable name).

If needed, I'm using R2022b MATLAB version.

I really appreciate your help. Best regards!

Answer 1

[Stephen23]

Assuming that the tables already exist:

table1 = table(["Smith";"Nguyen";"Williams";"Fernandez";"Brown"],[38;43;38;40;49], ...
    [71;69;64;67;64],[176;163;131;133;119]); % Randomly generated table1
table1.Properties.VariableNames = ["LastName","Age","Height","Weight"] % Adding headers

table1 = 5x4 table
     LastName      Age    Height    Weight
    ___________    ___    ______    ______

    "Smith"        38       71       176  
    "Nguyen"       43       69       163  
    "Williams"     38       64       131  
    "Fernandez"    40       67       133  
    "Brown"        49       64       119  

table2 = table(["James";"Mary";"Anna";"Jhon";"Pow"],[67;49;18;95;29],...
    [31;65;23;17;48],[90;16;63;13;33]); % Randomly generated table2
table2.Properties.VariableNames = ["LastName","Age","Height","Weight"] % Adding headers

table2 = 5x4 table
    LastName    Age    Height    Weight
    ________    ___    ______    ______

    "James"     67       31        90  
    "Mary"      49       65        16  
    "Anna"      18       23        63  
    "Jhon"      95       17        13  
    "Pow"       29       48        33  

Use curly-brace indexing to implicitly create the new column:

table1{:,'Source'} = "table1";
table2{:,'Source'} = "table2";
table3 = [table1;table2]

table3 = 10x5 table
     LastName      Age    Height    Weight     Source 
    ___________    ___    ______    ______    ________

    "Smith"        38       71       176      "table1"
    "Nguyen"       43       69       163      "table1"
    "Williams"     38       64       131      "table1"
    "Fernandez"    40       67       133      "table1"
    "Brown"        49       64       119      "table1"
    "James"        67       31        90      "table2"
    "Mary"         49       65        16      "table2"
    "Anna"         18       23        63      "table2"
    "Jhon"         95       17        13      "table2"
    "Pow"          29       48        33      "table2"

[Sara Woods]

Thanks so much! Indeed, my problem was adding a column to an already existing table!

Answer 2

[Aquatris]

You can add "Source" header to each table with "Table 1" or "Table 2" inputs and join them like joining arrays;

table1 = table(repelem("Table 1",5,1),["Smith";"Nguyen";"Williams";"Fernandez";"Brown"],[38;43;38;40;49], ...
          [71;69;64;67;64],[176;163;131;133;119]); % Randomly generated table1
table1.Properties.VariableNames = ["Source","LastName","Age","Height","Weight"]; % Adding headers
table2 = table(repelem("Table 2",5,1),["James";"Mary";"Anna";"Jhon";"Pow"],[67;49;18;95;29], ...
          [31;65;23;17;48],[16;63;13;33;176]); % Randomly generated table2
table2.Properties.VariableNames = ["Source","LastName","Age","Height","Weight"]; % Adding headers

table3 = [table1;table2]

table3 = 10x5 table
     Source       LastName      Age    Height    Weight
    _________    ___________    ___    ______    ______

    "Table 1"    "Smith"        38       71       176  
    "Table 1"    "Nguyen"       43       69       163  
    "Table 1"    "Williams"     38       64       131  
    "Table 1"    "Fernandez"    40       67       133  
    "Table 1"    "Brown"        49       64       119  
    "Table 2"    "James"        67       31        16  
    "Table 2"    "Mary"         49       65        63  
    "Table 2"    "Anna"         18       23        13  
    "Table 2"    "Jhon"         95       17        33  
    "Table 2"    "Pow"          29       48       176  

[Sara Woods]

Thanks! But, there is another way to add the header row "source" to table1 and table2 straightforwardly? This is, in another code line, not in the code line generating the tables

Answer 3

[Rahul]

Hi @Sara Woods,

I’m assuming that you’re trying to vertically concatenate two tables in MATLAB, into a new table, which contains an additional column stating the origin table of that specific row.

You can include an additional ‘origin’ column in both tables, which can later be incorporated in the concatenated table, showing the source table of that entry. Here’s how you can structure your code, to include the 'origin' column at the time of table generation:

% Generate table1 with a 'Source' column
table1 = table(["Smith";"Nguyen";"Williams";"Fernandez";"Brown"], [38;43;38;40;49], ...
    [71;69;64;67;64], [176;163;131;133;119], ...
    repmat("table1", 5, 1), 'VariableNames', ...
    ["LastName", "Age", "Height", "Weight", "Source"]);

% Generate table2 with a 'Source' column
table2 = table(["James";"Mary";"Anna";"John";"Pow"], [67;49;18;95;29], ...
    [31;65;23;17;48], [90;16;63;13;33], ...
    repmat("table2", 5, 1), 'VariableNames', ...
    ["LastName", "Age", "Height", "Weight", "Source"]);

% Merge the two tables vertically
table3 = vertcat(table1, table2)

table3 = 10x5 table
     LastName      Age    Height    Weight     Source 
    ___________    ___    ______    ______    ________

    "Smith"        38       71       176      "table1"
    "Nguyen"       43       69       163      "table1"
    "Williams"     38       64       131      "table1"
    "Fernandez"    40       67       133      "table1"
    "Brown"        49       64       119      "table1"
    "James"        67       31        90      "table2"
    "Mary"         49       65        16      "table2"
    "Anna"         18       23        63      "table2"
    "John"         95       17        13      "table2"
    "Pow"          29       48        33      "table2"

For more information regarding the functions mentioned above, refer to the following documentation links:

• Repeat copies of array using “repmat” function: https://www.mathworks.com/help/matlab/ref/repmat.html
• Concatenate arrays vertically using “vertcat” function: https://in.mathworks.com/help/matlab/ref/double.vertcat.html

[Sara Woods]

Thanks! But, if I want to add a header 'Source' with my desired variable 'table1' to the already existing table1, how could I code it? Thanks again!