It is a temporary description. {traccr} is under development, with
limited functionality
The {traccr} is an R package to calculate (transport) accessibility
from origin-destination matrices. Its advantage is that it allows for a
flexibility in terms of structure of the source data: OD matrices as
well as the data on destination attractiveness.
It uses {data.table} for
efficient computations and it is created based on several tailored
scripts I used for working with ArcGIS Network Analyst outputs, but it
should work with
e.g. OpenTripPlanner, or
any other origin-destination matrices as well.
if(!"devtools" %in% rownames(installed.packages()))
install.packages("devtools")
devtools::install_github("stmarcin/traccr")The main advantage of the {traccr} is that it permits to compute basic
accessibility indicators while accepting different types of file
structure and the way the data is stored.
In the OD file, the ids of origins and destinations can be stored in two
different columns or in one column coded e.g. as origin_id - destination_id. In case of the latter, {traccr} would take care of
splitting the data in the background. User can define pattern used for
splitting (in a given example it would be - which is also a default
option).
As calculation of OD matrices is usually the most time-consuming process
in any accessibility analysis, it makes sense to prepare even larger
ones to cover all possible links and then to select only required
ones in the analysis. This prevents from re-calculating OD matrices and
I applied it, e.g. in the
GIService project which
focuses on accessibility to public services in Poland.
In this case, the OD matrix is filtered based on the data set of
destinations stored in a separate file. {traccr} would conduct an
inner join to filter out all irrelevant trips from OD matrix and
provide results for desired set of destinations.
see this vignette for details (to be prepared)
Accessibility indicators usually consider quantified attractiveness of
destinations (e.g. number of jobs in the area, number of medical doctors
etc.) and that data is usually stored in a separate file. As in case of
selection of destinations, {traccr} merges OD matrix with destinations
data and compute desired accessibility indicator (cumulative
opportunities, potential accessibility). See vignettes for details
(to be prepared).
(to be prepared)
(to be prepared)
Proximity, also known as distance or travel time to the nearest provider
Cumulative opportunities accessibility measure, also known as isochronic measure