How to combine two tables with same variable name without change anything in the table

Question

Sandy Woo 2018-12-21

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此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/436818-how-to-combine-two-tables-with-same-variable-name-without-change-anything-in-the-table

评论： Peter Perkins 2019-3-14

I have performed a lot of experiments and got over 50 xlsx files with over 10 arrays data in it, and each of them has the same variable names and datas, such as:

1. Experiment 1: made at 2018, the injection rate is 0.146ml/min

The content in the xlsx flie which was recored is:

        Slice                   Time      X        Y
2018-bz-10-0.146-001.png        0.1    123.10  155.84 
2018-bz-10-0.146-002.png        0.3    115.28  155.443
2018-bz-10-0.146-003.png        0.6    116.36  155.406 

2. Experiment 2: made at 2018, the injection rate is 2.128ml/min

The content in the xlsx flie which was recored is:

        Slice                   Time     X       Y
2018-bz-10-2.128-001.png        18.5   11.68   128.08
2018-bz-10-2.128-002.png        36.4   130.89  155.4

P.S. The second file just have two slices as the camera for the image slices stops earlier.

I use 'readtable' to import these xlsx files. As there are too much of them, I decide to combine all of the xlsx into one parallel table, and save it as one xlsx. Just like

        Slice                   Time     X       Y              Slice                   Time      X        Y
2018-bz-10-2.128-001.png        18.5   11.68   128.08     2018-bz-10-0.146-001.png      0.1    123.10  155.84 
2018-bz-10-2.128-002.png        36.4   130.89  155.4      2018-bz-10-0.146-002.png      0.3    115.28  155.443
2018-bz-10-2.128-003.png        45.4    NaN     NaN       

Therefore, depend on this single xlsx, I can efficiently organize my datasets and copy these data to other places, while any of the data in it could be traced to its original source. Furthermore, I could modify the .m to particularly extract two arrays in all xlsx into one xlsx for further comparisons.

So could any help me about this? It seems just a simple combination of data, but matlab told me

Cannot find a common table variable to use as a key variable.

Or:

Duplicate variable name: 'Slice'.

So any solutions? Thanks!

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Sandy Woo 2019-3-14

在 MATLAB Online 中打开

Hi Peter

Thank you very much for your reply! The situation is that I have performed over 50 sets of experiments, and record the parameters of each of them, which were stored in different xlsx files. Now I wish to combine them together into one xlsx file, e.g. the 1.xlsx and 2.xlsx into 3.xlsx. So how could I do that in matlab?

I try to combine the two tables side-by-side so that I could plot them as the format of 'xyxy'. In my experiments, I cannot ensure the measurement time for each set of experiments is equivalent. Some experiments just started earlier. So the xlsx files have different numbers of rows. I wrote the code like:

A = readtable('C:\Users\s\Desktop\1.xlsx');
B = readtable('C:\Users\s\Desktop\2.xlsx');
C = cat(2,A(:,2),A(:,3),B(:,2),B(:,3));

But matlab warns like:

Error using tabular/cat (line 14)
All tables in the bracketed expression must have the same number of rows.

So how could I achieve a matrix of table like 3.xlsx? Thanks a lot for this!

Peter Perkins 2019-3-14

在 MATLAB Online 中打开

This question doesn't make sense to me. Here are your two tables:

>> A = readtable('1.xlsx')
A =
  3×4 table
               Slice                Time      X         Y   
    ____________________________    ____    ______    ______
    {'2018-bz-10-0.146-001.png'}    0.1      123.1    155.84
    {'2018-bz-10-0.146-002.png'}    0.3     115.28    155.44
    {'2018-bz-10-0.146-003.png'}    0.6     116.36    155.41
>> B = readtable('2.xlsx')
B =
  2×4 table
               Slice                Time      X         Y   
    ____________________________    ____    ______    ______
    {'2018-bz-10-2.128-001.png'}    18.5     11.68    128.08
    {'2018-bz-10-2.128-002.png'}    36.4    130.89     155.4

They have no values in common on which to join them, nor do they have the same number of rows. I don't see any way to sensibly put them side-by-side.

If you want something otyher than

>> [A; B]
ans =
  5×4 table
               Slice                Time      X         Y   
    ____________________________    ____    ______    ______
    {'2018-bz-10-0.146-001.png'}     0.1     123.1    155.84
    {'2018-bz-10-0.146-002.png'}     0.3    115.28    155.44
    {'2018-bz-10-0.146-003.png'}     0.6    116.36    155.41
    {'2018-bz-10-2.128-001.png'}    18.5     11.68    128.08
    {'2018-bz-10-2.128-002.png'}    36.4    130.89     155.4