Problems with Tables which contain a single row.

Question

Matt O'Brien 2022-8-28

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此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/1789220-problems-with-tables-which-contain-a-single-row

评论： Matt O'Brien 2022-8-28

I have a GUI app working and just doing final testing. Everything is working very well..... except when I encounter a scenario where a table has a single row.

I have replicated the scenario with the following example...

Table3Rows has 3 rows and 3 columns. Table1Row is the same as Table3Rows but only contains the first row.

clc
var1 = ['abc';'def';'ghi'];
var2 = [1;2;3];
var3 = ['x';'y';'z'];
Table3Rows = table(var1,var2,var3) % This table has 3 rows
Table1Row = Table3Rows(1,:) % Same as table above but wth just the first row
TableVar1 =table(Table3Rows.var1) % This works perfectly (ie create a new table with just the first column)
TableVar1Row1 = table(Table1Row.var1) % This is identical except Table1Row has only 1 row but causes an error

The last 2 instructions are identical. The last instruction creates an error.

In a real world scenario, I cannot control how many rows may be in the table. It may be empty, 1, 10,1000's.

Any hints on how I can cater for the single row (within a table) scenario.

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Answer 1

Matt O'Brien 2022-8-28

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https://ww2.mathworks.cn/matlabcentral/answers/1789220-problems-with-tables-which-contain-a-single-row#answer_1036280

在 MATLAB Online 中打开

What a super quick response.... really appreciated.

I have refined your version as follows. I prefer to use the column variable names .... as the tables in use have 15-20 columns and the design is still evolving... Too difficult to debug if one of the columns moves relative to the others...

clc
var1 = ['abc';'def';'ghi'];
var2 = [1;2;3];
var3 = ['x';'y';'z'];
Table3Rows = table(var1,var2,var3) % This table has 3 rows
Table1Row = Table3Rows(1,:) % Same as table above but wth just the first row
% TableVar1 = Table3Rows(:, 1) % Extract only the first column into a new table.
% TableVar1Row1 = Table1Row(:, 1) % Extract only the first column into a new table.
TableVar1 = Table3Rows(:, "var1") % Extract only the first column into a new table.
TableVar1Row1 = Table1Row(:, "var1") % Extract only the first column into a new table.

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Answer 2

Image Analyst 2022-8-28

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此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/1789220-problems-with-tables-which-contain-a-single-row#answer_1036275

在 MATLAB Online 中打开

Don't use table(). Try it using indexing:

var1 = ['abc';'def';'ghi'];
var2 = [1;2;3];
var3 = ['x';'y';'z'];
Table3Rows = table(var1,var2,var3) % This table has 3 rows
Table1Row = Table3Rows(1,:) % Same as table above but wth just the first row
TableVar1 = Table3Rows(:, 1) % Extract only the first column into a new table.
TableVar1Row1 = Table1Row(:, 1) % Extract only the first column into a new table.