MATLAB: How to import data from .xls using for Principal Component Analysis (PCA)

pcaprincipal component analysisStatistics and Machine Learning Toolbox

Hello,
I have a worksheet in excel that contains the following data:
17 rows x 5 columns of data – the first row contains the title 3 of the variables (names of 3 different people), meanwhile column 1 contains the title for the 16 different possibilities. the internal matrix, which ends up being a 16×4, contains the statistic. I import the data into Matlab, but don't know if i should import as a matrix, cell array, or dataset. From there, how do I perform PCA? I want it to contain the names of the variables.
So far, I've performed this:
>> coeff = princomp(Cocktail1)
coeff =
    0.0453    0.9976    0.0500   -0.0130
    0.4413   -0.0662    0.8831   -0.1453
    0.5300   -0.0067   -0.1275    0.8383
    0.7227   -0.0172   -0.4489   -0.5253
However, the problem is it does not show me titles of the variables.
Thank you.

Best Answer

Michelle, your approach is correct. princomp (or pca which is a newer and recommended function to use) accepts only matrices as inputs, and returns the principal component coefficients as the first output.
It is important to note however, that pca transforms your data to a new coordinate space. This means your original variable names don't make much sense for your transformed data. The second output of pca is the transformed data which is a linear combination of your original data:
http://www.mathworks.com/help/stats/pca.html
If you want to simple assign some names to them, I recommend using Table as follows:
T = array2table(coeff,'VariableNames',{'Name1' 'Name2' 'Name3' 'Name4'})
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