> $ opam install gnuplot
The following dependencies couldn't be met:
  - gnuplot -> core < v0.9.0 -> sexplib < 113.25.00
  - gnuplot -> core < v0.9.0 -> ppx_jane < 113.34.00 -> ppx_sexp_message < 113.34.00+4.03 -> ppx_core < 113.34.00+4.03
  - gnuplot -> core < v0.9.0 -> ppx_jane < 113.34.00 -> ppx_typerep_conv < 113.25.00 -> ppx_core < 113.25.00
  - gnuplot -> core < v0.9.0 -> ppx_bench < 113.34.00+4.03 -> ppx_core < 113.34.00+4.03
Your request can't be satisfied:
  - core<=113.00.00 is not available because your system doesn't comply with ocaml-version >= "4.02.1" & ocaml-version < "4.03".
  - ppx_core<113.25.00 is not available because your system doesn't comply with ocaml-version >= "4.02.3" & ocaml-version < "4.03.0".
  - ppx_core<113.34.00+4.03 is not available because your system doesn't comply with ocaml-version = "4.02.3".
  - sexplib<113.25.00 is not available because your system doesn't comply with ocaml-version >= "4.02.3" & ocaml-version < "4.03.0".