Help normalizing data in table

18 views (last 30 days)
Nina Perf
Nina Perf on 3 Dec 2021
Edited: Nina Perf on 3 Dec 2021
Hi,
I have a 100x6 Table with 6 variables. I want to center the data so that it has mean 0 and standard deviation 1, using the zscore.
I tried using this in the 3 variables of interest but is not working.
Normalized = normalize(data(:,1:3)));
If I try to convert the table to array then I loose the table information.
Thank you in advance!

Accepted Answer

Dave B
Dave B on 3 Dec 2021
Edited: Dave B on 3 Dec 2021
When you want to work with multiple variables in a table at once, you have to use { } (this is because tables work with heterogenous data)
data=table(10*randn(100,1)+5, randn(100,1)/10, randn(100,1).^2);
ndata = data(:,1:3);
ndata{:,1:3} = normalize(ndata{:,1:3});
round(mean(table2array(ndata)),-10)
ans = 1×3
0 0 0
std(table2array(ndata))
ans = 1×3
1.0000 1.0000 1.0000
  3 Comments
Dave B
Dave B on 3 Dec 2021
For the round bit - that's just because (after normalizing) the mean is close to zero, but not exactly zero. I rounded it to 10 digits. Here's what it looks like without the round:
data=table(10*randn(100,1)+5, randn(100,1)/10, randn(100,1).^2);
ndata = data(:,1:3);
ndata{:,1:3} = normalize(ndata{:,1:3});
mean(table2array(ndata))
ans = 1×3
1.0e+-15 * -0.0844 0.0266 -0.1821
So that's like -0.0000000000000000844 for the first one (I might have miscounted my zeros!)
I'm not sure what you mean by the std is not 1, can you give an example? (similar to the means, they're not exactly 1, but I'd think would be close to 1). Note that you can also use zscore in place of normalize, I just wanted to help with the 'how to apply it to table' bit...but I'd expect zscore and normalize to produce the same results...
Nina Perf
Nina Perf on 3 Dec 2021
Edited: Nina Perf on 3 Dec 2021
Thank you! The zscore function works well. However, the normalize function gives std close to 0..

Sign in to comment.

More Answers (0)

Products


Release

R2021a

Community Treasure Hunt

Find the treasures in MATLAB Central and discover how the community can help you!

Start Hunting!