Adding a column of the same character name for all the rows in a table
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Aaron Devanathan
il 9 Apr 2021
Risposto: Peter Perkins
il 3 Mar 2022
I have a table in MATLAB that I'd like to add a column that contains a character variable that's the same throughout the column, but different size lengths. Here's a code for two random tables.
Is there a way, for example, for me to add a column named 'Time' that contains the character 'hours' for both based on the number of rows of the table?
r1 = rand(100,1);
r1 = array2table(r1);
r1.Properties.VariableNames = {'Random1'};
r2 = rand(54,1);
r2 = array2table(r2);
r2.Properties.VariableNames = {'Random2'};
1 Commento
Abhishek Gupta
il 12 Apr 2021
Hi,
As per my understanding, you want to add a column to the existing table. You can do the same in the following way: -
r1 = rand(100,1);
r1 = array2table(r1);
r1.Properties.VariableNames = {'Random1'};
strs1 = repmat('hours', size(r1, 1), 1);
vTbl1 = table(strs1, 'VariableNames',{'Time'});
r1 = [r1, vTbl1];
r2 = rand(54,1);
r2 = array2table(r2);
r2.Properties.VariableNames = {'Random2'};
strs2 = repmat('hours', size(r2, 1), 1);
vTbl2 = table(strs2, 'VariableNames',{'Time'});
r2 = [r2, vTbl2];
Risposta accettata
Scott MacKenzie
il 13 Mag 2021
From my understanding of the question, this is simply a matter of making the necessary assignment to r1.Time or r2.Time. Do so and a new column with variable name Time is automatically appended to the table:
r1 = rand(100,1);
r1 = array2table(r1);
r1.Properties.VariableNames = {'Random1'};
r1.Time = repmat({'hours'}, height(r1), 1);
r2 = rand(54,1);
r2 = array2table(r2);
r2.Properties.VariableNames = {'Random2'};
r2.Time = repmat({'hours'}, height(r2), 1);
Here's a command-window dump of the first 8 rows in the new r1:
>> head(r1)
ans =
8×2 table
Random1 Time
_________ _________
0.49707 {'hours'}
0.32079 {'hours'}
0.61628 {'hours'}
0.0068941 {'hours'}
0.062934 {'hours'}
0.92002 {'hours'}
0.90616 {'hours'}
0.83154 {'hours'}
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Più risposte (1)
Peter Perkins
il 3 Mar 2022
It's even simpler than that:
>> r1 = array2table(rand(5,1),'VariableNames',"Random1");
>> r1.Time(:) = "hours"
r1 =
5×2 table
Random1 Time
_______ _______
0.31907 "hours"
0.98605 "hours"
0.71818 "hours"
0.41318 "hours"
0.09863 "hours"
It's not clear what you would do with this variable, though. I'm gonna take a guess that at some point you will end up vertically concatenating these tables and the text will be different in different tables (except right now, you can't because your var names are different). In that case, use categorical, not text.
>> r1 = array2table(rand(2,1),'VariableNames',"X");
>> r1.Time(:) = categorical("hours")
r1 =
2×2 table
X Time
_______ _____
0.73456 hours
0.63731 hours
>> r2 = array2table(rand(3,1),'VariableNames',"X");
>> r2.Time(:) = categorical("days")
r2 =
3×2 table
X Time
________ ____
0.073842 days
0.12051 days
0.9816 days
>> [r1; r2]
ans =
5×2 table
X Time
________ _____
0.73456 hours
0.63731 hours
0.073842 days
0.12051 days
0.9816 days
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