US House Price Index Analysis

In the past, I used MiniTab or SPSS to analyse Los Angeles Metro House Price. I also want to analyse all the 401 US Metors' House Price. But it need batch script program to achieve this.
Last yeas, I took the INTRO TO DATA SCIENCE workshop from mysliderule.com. And I found that I can easily to do analyse all the US Metros HPI at a time by using R.
I collected the HPI quarterly data from year 1975 to now. And do a simple exponential regression.
The result looks pretty good. It can easily to show when is a good or not good timing to buy a house. I hope this analysis can be your reference.

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You can view all the 401 US Metros House Price Index analysis by click the following link.
US HPI Analysis

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We are assume the residual is or most like normal distribution.
Basic on our assume, there should be around 70% of HPI data points locate between the green line and orange line.
Around 15% of HPI data points locate under the green line. On the other words, less than 15% of chance that the HPI lower this green line.
Around 15% of HPI data points locate upper the orange line. On the other words, less than 15% of chance that the HPI higher this orange line.

HPI Example

Data From : http://www.fhfa.gov; http://www.freddiemac.com