Inductive effect of alkyl ammonium groups Why $\ce{-NR3+}$ has more -I effect than $\ce{-NH3+}?$
And what about order of $\ce{-NHR2+}$ and $\ce{-NH2R+}?$

My attempts
I got idea about electronegativity of carbon atom in $\ce{R}$ is more than hydrogen atom, hence positive charge gets more concentrated on nitrogen atom and it exerts more electronic attraction. But this didn't worked out in latter case when -I effect of $\ce{-NHR2+}$ is less than $\ce{-NH2R+}.$
The inductive effect is both distance-dependent and &chi;-dependent. N-H bonds are 1.01 Å, yet the &chi; of H is only 2.1. N-C bonds are 1.42 Å, yet the &chi; of C is 2.5. At the extremes, where there are only N-C or N-H bonds, the ordering of -I is easy to rationalize.

However, the two, short N-H bonds in -NH2R+ outweigh the higher &chi; of N-C bonds, giving -NH2R+ a higher -I than -NHR2+.