Merge pull request #79 from SpatLyu/dev

polish readme

Author: SpatLyu

README.md

@@ -42,7 +42,7 @@ install.packages("infoxtr",
 - Install from source code on [GitHub](https://github.com/stscl/infoxtr) with:
 
 ``` r
-if (!requireNamespace("devtools")) {
+if (!requireNamespace("devtools", quietly = TRUE)) {
     install.packages("devtools")
 }
 devtools::install_github("stscl/infoxtr",
@@ -52,12 +52,20 @@ devtools::install_github("stscl/infoxtr",
 
 ## References
 
-Schreiber, T., 2000. Measuring Information Transfer. Physical Review Letters 85, 461–464. https://doi.org/10.1103/physrevlett.85.461.
+Schreiber, T., 2000. Measuring Information Transfer. Physical Review Letters 85, 461–464. [https://doi.org/10.1103/physrevlett.85.461][1].
 
-Kraskov, A., Stogbauer, H., Grassberger, P., 2004. Estimating mutual information. Physical Review E 69. https://doi.org/10.1103/physreve.69.066138.
+Kraskov, A., Stogbauer, H., Grassberger, P., 2004. Estimating mutual information. Physical Review E 69. [https://doi.org/10.1103/physreve.69.066138][2].
 
-Martinez-Sanchez, A., Arranz, G., Lozano-Duran, A., 2024. Decomposing causality into its synergistic, unique, and redundant components. Nature Communications 15. https://doi.org/10.1038/s41467-024-53373-4.
+Martinez-Sanchez, A., Arranz, G., Lozano-Duran, A., 2024. Decomposing causality into its synergistic, unique, and redundant components. Nature Communications 15. [https://doi.org/10.1038/s41467-024-53373-4][3].
 
-Zhang, X., Chen, L., 2025. Quantifying interventional causality by knockoff operation. Science Advances 11. https://doi.org/10.1126/sciadv.adu6464.
+Zhang, X., Chen, L., 2025. Quantifying interventional causality by knockoff operation. Science Advances 11. [https://doi.org/10.1126/sciadv.adu6464][4].
 
-Varley, T.F., 2025. Information theory for complex systems scientists: What, why, and how. Physics Reports 1148, 1–55. https://doi.org/10.1016/j.physrep.2025.09.007.
+Varley, T.F., 2025. Information theory for complex systems scientists: What, why, and how. Physics Reports 1148, 1–55. [https://doi.org/10.1016/j.physrep.2025.09.007][5].
+
+ 
+
+[1]: https://doi.org/10.1103/physrevlett.85.461
+[2]: https://doi.org/10.1103/physreve.69.066138
+[3]: https://doi.org/10.1038/s41467-024-53373-4
+[4]: https://doi.org/10.1126/sciadv.adu6464
+[5]: https://doi.org/10.1016/j.physrep.2025.09.007