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Showing posts from October, 2015

First post using stackedit

Welcome to StackEdit! Hey! I’m your first Markdown document in StackEdit 1 . Don’t delete me, I’m very helpful! I can be recovered anyway in the Utils tab of the Settings dialog. Documents StackEdit stores your documents in your browser, which means all your documents are automatically saved locally and are accessible offline! Note: StackEdit is accessible offline after the application has been loaded for the first time. Your local documents are not shared between different browsers or computers. Clearing your browser’s data may delete all your local documents! Make sure your documents are synchronized with Google Drive or Dropbox (check out the Synchronization section). Create a document The document panel is accessible using the button in the navigation bar. You can create a new document by clicking New document in the document panel. Switch to another document All your local documents are listed in the document panel. You can switch from one to anoth...

Testing the difference between two correlations in R

Introduction Correlation is the measurement to measure how two datasets increase or decrease together. It's a real number range from -1 (i.e, when one dataset increases, another one decreases and vice versa) to +1 (i.e, these two datasets increase or decrease together). Value 0 means there is no relationship between two datasets. Calculating correlation Calculating correlation of two datasets in R is quite straightforward: In R: > x = c (1,5,2,6,7) > y = c (2,4,3,9,-5) > cor(x,y) [1] -0.1459338 Usually, a single value does not say much in statistics. You need a confidence level. > cor.test (x, y) Pearson's product-moment correlation data:  x and y t = -0.2555, df = 3, p-value = 0.8149 alternative hypothesis: true correlation is not equal to 0 95 percent confidence interval:  -0.9109173  0.8451475 sample estimates:        cor  -0.1459338  The function 'cor.test' will gives you the correlation, ...