Data matrix expression file is a Tab-separated values file.

A tab-separated values (TSV) file is a simple text format for storing data in a tabular structure (e.g. database or spreadsheet data). Each record in the table is one line of the text file. Each field value of a record is separated from the next by a tab stop character. More about TSV...

This file has two columns if there is only one sample, and more than two columns if there are many samples. First line is a header and must contain the sample names. The first column correspond to gene, probe or protein Ids from:

1. Ensembl gene
2. HGNC symbol
3. Entrez id
4. Affy HG U133A probeset
5. Affy HG U133B probeset
6. Affy HG U133-PLUS-2 probeset
7. Affy HTA 2.0

The next columns correspond to gene expression values in numeric format from each sample.

Here is an example of a file with only one example:

expression.txt

id	sampleName
1	0.3
2	1
3	0.73

And here is another example with more than one sample:

expression-multi.txt

id	sample1	sample2	sample3
1	0.31	0.6	0.24
2	1	0.81	0.91
3	0.7	0.9	0.3
4	0.23	0.45	0.33

Here you can download real example file: