Add README.

Author: ntthung

README.md

@@ -0,0 +1,57 @@
+# Mass Balance Regression
+
+This package implements the Mass-balance-adjusted regression algorithm for sub-annual streamflow reconstruction. The algorithm implements a penalty term to minimize the differences between the total seasonal flow reconstruction and the annual flow reconstruction. Details are presented in Nguyen et al (2020).
+
+Currently the package is only available on GitHub, but it will be available on CRAN soon.
+
+To install the development from GitHub
+
+``` {.r}
+install.packages('remotes')
+remotes::install_github('ntthung/mbr')
+```
+
+The package has two main functions, `mb_reconstruction()` for reconstruction, and `cv_mb()` for cross-validation.
+
+Example reconstruction
+
+``` {.r}
+fit <- mb_reconstruction(
+  instQ = p1Seasonal,
+  pc.list = pc3seasons,
+  start.year = 1750,
+  lambda = 1,
+  log.trans = 1:3
+)
+```
+
+Example cross-validation
+
+``` {.r}
+# Create hold-out chunks
+set.seed(24)
+cvFolds <- make_Z(
+  obs = 1922:2003,
+  nRuns = 50, 
+  frac = 0.25,
+  contiguous = TRUE
+)
+# Run cross validation
+cv <- cv_mb(
+  instQ = p1Seasonal,
+  pc.list = pc3seasons,
+  cv.folds = cvFolds,
+  start.year = 1750,
+  lambda = 1,
+  log.trans = 1:3,
+  return.type = 'metric means'
+)
+# Round up to two decimal places
+cv[, (2:6) := lapply(.SD, round, digits = 2), .SDcols = 2:6][]
+```
+
+Type \`browseVignettes('mbr') for details.
+
+**References**
+
+Nguyen, H. T. T., Galelli, S., Xu, C., & Buckley, B. (2020). Multi-Proxy, Multi-Season Streamflow Reconstruction with Mass Balance Adjustment. Earth and Space Science Open Archive, 22. <https://doi.org/10.1002/essoar.10504791.1>