[R] How to swap and rearrange rows?

[Roslina Zakaria]

Dear R-expert,
How to swap and rearrange the row so that I will have
Jan-Dec in order?
> est31
            p0 est.alpha est.beta  est.rate
Jan  0.8802867 0.7321440 7.241757 0.1380880
Mar  0.8598566 0.7096567 7.376367 0.1355681
May  0.6204301 0.8657272 6.036106 0.1656697
July 0.5032258 0.9928488 4.027408 0.2482986
Aug  0.5322581 0.9625738 4.103121 0.2437169
Oct  0.6792115 0.8526226 5.105218 0.1958780
Dec  0.8397849 0.7490287 7.070349 0.1414357
> est30
            p0 est.alpha est.beta  est.rate
Apr  0.7296296 0.7929348 6.303877 0.1586325
Jun  0.5574074 0.8588608 5.695905 0.1755647
Sept 0.6066667 0.9031150 4.594891 0.2176330
Nov  0.7725926 0.7600906 5.636366 0.1774193
> est28
          p0 est.alpha est.beta  est.rate
Feb 0.877262 0.6567584 8.708051 0.1148363
Thank you so much.