
All the data used in this study is 
available at \protect\url{http://promisedata.org/data} or from the
authors.
%Our data sets are very heterogenous (observe their 60-fold variation in the skewness from 0.86 to 6.6).
As shown in \fig{datasets}, data is from
(a) various geographical locations;
(b) contain various instance and feature sizes;
and (c) have high divergence of features describing the software projects.
%For example,
%the COCOMO* and NASA* data sets all use the features defined by Boehm~\cite{Boehm1981}; e.g.
%analyst capability, required software reliability, memory constraints, and use of software tools.
%The other data sets use a wide variety of features including, number of entities in the data model, number of basic logical transactions, query count, number of distinct business units serviced etc.

As to other details about our data:
\bi
\item COCOMO81 and NASA93 are standard COCOMO data sets. Criterion for subsets in NASA93 is the development centers (center\_1, center\_2 and center\_5) and in COCOMO81 it is the development mode (embedded, organic and semi-detached).
\item Subsets of DESHARNAIS contain projects developed in different languages.
\item SDR is a dataset that includes projects of various software companies from Turkey~\cite{Bakir2009};
\item The CHINA dataset is one of the largest publicly available datasets with 499 instances. It includes software projects developed in China by various software companies in multiple business domains.
\ei

%Note that two of these data sets (Nasa93c2, Nasa93c5)
%come from different development centers around the United States. Another two of these
%data sets (Cocomo81e, Cocomo81o) represent different kinds of projects:
%\bi
%\item The Cocomo81e  ``embedded projects''
%are those developed within tight constraints (hardware, software, operational, ...);
%\item
%The Cocomo81o ``organic projects'' come from
%small teams with good experience of working with less than rigid requirements.
%\ei




