Concatenate a string array and a table of different dimensions

I have a txt which that has two parts (see the txt attached): an non-editable header (in the file attached, everyline that has a # as first charater), followed by a tab-delimited table. To replace some of the values in the table, I have imported the table in matlab by doing the following:

table = readtable('data.txt');

The command above will skip the header section of the file and import the table as expected. I then replaced the values.

Problem: What I need to do now, is to paste the table below the header section of the original file and save it as a txt file. This part is essential for the file to be properly read in the package I'm using to run my analyses. This is where I got stuck and can't seem to find a way out. It seems to me that the header can only be imported in MATLAB as a string array by doing the following:

header = readlines('data.txt');
header = header(1:24, :);

So, I have been trying to turn the table into a string array, so it could be pasted below header. On the one hand, if I try to do that:

tableArray = table2array(table);

The tableArray object has more dimensions (= columns) that the header object, so they can't be concatenated. On the other hand, if I try to reduce the dimensions of tableArray, the columns of the tables are merged together, which will make it impossible to use the file for later analyses.

I am not a Matlab expert and I've run out of options. I would really appreciate some help -- even a suggestion -- with this.

Thank you in advance!

Answer 1

[Seth Furman]

writematrix and writetable both take a 'WriteMode' name-value pair that can be set to 'append'. To write a header followed by a table, you can use writematrix to write your file header and then writetable(__,'WriteMode','append') to append the table data to the same file.

https://www.mathworks.com/help/matlab/ref/writematrix.html#mw_f36f6f84-e6bd-4749-8957-a88b07036116

https://www.mathworks.com/help/matlab/ref/writetable.html?searchHighlight=writetable&s_tid=srchtitle#mw_ebe3afac-7551-491c-8210-41c3c5393141

For example,

>> t = readtable('patients.xls');
>> t = head(t)

t =

  8×10 table

      LastName        Gender      Age              Location               Height    Weight    Smoker    Systolic    Diastolic    SelfAssessedHealthStatus
    ____________    __________    ___    _____________________________    ______    ______    ______    ________    _________    ________________________

    {'Smith'   }    {'Male'  }    38     {'County General Hospital'  }      71       176      true        124          93             {'Excellent'}      
    {'Johnson' }    {'Male'  }    43     {'VA Hospital'              }      69       163      false       109          77             {'Fair'     }      
    {'Williams'}    {'Female'}    38     {'St. Mary's Medical Center'}      64       131      false       125          83             {'Good'     }      
    {'Jones'   }    {'Female'}    40     {'VA Hospital'              }      67       133      false       117          75             {'Fair'     }      
    {'Brown'   }    {'Female'}    49     {'County General Hospital'  }      64       119      false       122          80             {'Good'     }      
    {'Davis'   }    {'Female'}    46     {'St. Mary's Medical Center'}      68       142      false       121          70             {'Good'     }      
    {'Miller'  }    {'Female'}    33     {'VA Hospital'              }      64       142      true        130          88             {'Good'     }      
    {'Wilson'  }    {'Male'  }    40     {'VA Hospital'              }      68       180      false       115          82             {'Good'     }      

>> writematrix(["BEGIN HEADER";"Header line 1";"Header line 2";"END HEADER";""],'myfile.txt')
>> type myfile.txt

BEGIN HEADER
Header line 1
Header line 2
END HEADER

>> writetable(t,'myfile.txt','WriteMode','append','WriteVariableNames',true);
>> type myfile.txt

BEGIN HEADER
Header line 1
Header line 2
END HEADER

LastName,Gender,Age,Location,Height,Weight,Smoker,Systolic,Diastolic,SelfAssessedHealthStatus
Smith,Male,38,County General Hospital,71,176,1,124,93,Excellent
Johnson,Male,43,VA Hospital,69,163,0,109,77,Fair
Williams,Female,38,St. Mary's Medical Center,64,131,0,125,83,Good
Jones,Female,40,VA Hospital,67,133,0,117,75,Fair
Brown,Female,49,County General Hospital,64,119,0,122,80,Good
Davis,Female,46,St. Mary's Medical Center,68,142,0,121,70,Good
Miller,Female,33,VA Hospital,64,142,1,130,88,Good
Wilson,Male,40,VA Hospital,68,180,0,115,82,Good
>> readtable('myfile.txt')

ans =

  8×10 table

      LastName        Gender      Age              Location               Height    Weight    Smoker    Systolic    Diastolic    SelfAssessedHealthStatus
    ____________    __________    ___    _____________________________    ______    ______    ______    ________    _________    ________________________

    {'Smith'   }    {'Male'  }    38     {'County General Hospital'  }      71       176        1         124          93             {'Excellent'}      
    {'Johnson' }    {'Male'  }    43     {'VA Hospital'              }      69       163        0         109          77             {'Fair'     }      
    {'Williams'}    {'Female'}    38     {'St. Mary's Medical Center'}      64       131        0         125          83             {'Good'     }      
    {'Jones'   }    {'Female'}    40     {'VA Hospital'              }      67       133        0         117          75             {'Fair'     }      
    {'Brown'   }    {'Female'}    49     {'County General Hospital'  }      64       119        0         122          80             {'Good'     }      
    {'Davis'   }    {'Female'}    46     {'St. Mary's Medical Center'}      68       142        0         121          70             {'Good'     }      
    {'Miller'  }    {'Female'}    33     {'VA Hospital'              }      64       142        1         130          88             {'Good'     }      
    {'Wilson'  }    {'Male'  }    40     {'VA Hospital'              }      68       180        0         115          82             {'Good'     } 

[Roberto Petrosino]

Thanks! This seems to work!

Answer 2

[Steven Lord]

I'd probably store that information in the Description property of the table.

T = array2table(magic(4));
T.Properties.Description = "A table array created from the magic(4) matrix";

This information is not displayed when the table is displayed normally, but it can be seen using the summary function.

disp(T)

    Var1    Var2    Var3    Var4
    ____    ____    ____    ____

     16       2       3      13 
      5      11      10       8 
      9       7       6      12 
      4      14      15       1 

summary(T)

Description:  A table array created from the magic(4) matrix

Variables:

    Var1: 4x1 double

        Values:

            Min           4   
            Median        7   
            Max          16   

    Var2: 4x1 double

        Values:

            Min           2   
            Median        9   
            Max          14   

    Var3: 4x1 double

        Values:

            Min           3   
            Median        8   
            Max          15   

    Var4: 4x1 double

        Values:

            Min           1   
            Median       10   
            Max          13   

s = T.Properties.Description

s = 'A table array created from the magic(4) matrix'

[Roberto Petrosino]

Hi, thanks for replying!

If I try to do what you suggested, but I don't think it works for two reasons.

First, data.Properties.Description needs the Description property to be a string or a character vector. On the other hand, the header needs to be extracted by line number from the original file data.txt. This means that the data must be imported in matlab as a string array (I used readlines). If I try to do what you suggested, an error pops up:

header = readlines(/Users/user/Desktop/data.txt');
header = header(1:20,:);
data = readtable(/Users/user/Desktop/data.txt');
data.Properties.Description = header;
> The Description property must be a string or a character vector.

Second, even if I manage to store the header in the Description property of the table, how to do I print the whole thing (header + modified table) in a txt file?

Thanks!!