On 6 Jan 1997 02:48:10 -0800, athel at IR2CBM.CNRS-MRS.FR (Athel) wrote:
I recently made an informal poll of several colleagues about whether
they preferred to write control coefficients and elasticities in the
logarithmic form, i.e. ...........etc
My response when Athel asked me was:
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Although I started off using the fractional form, I now prefer the
log form (I don't think students should have too much difficulty with
it). The reason is not so much ease of printing, but that it forces
one to think in terms of slopes of log-log graphs and to present your
data directly in log-log form, which is much more useful for
interpretation than unscaled graphs and slopes.
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Allow me to put this more strongly:
To my mind there is no question that for the biological interpretation
of experimental results the scaled form of the coefficients of
control analysis is the correct form (it has been argued that the
unscaled form is preferable [Reder (1988) J. Theor. Biol. 135,
175-201], but this was more in the context of mathematics than biology
- I have set out my arguments for preferring the scaled form in
Hofmeyr (1996) J. Bioenerg. Biomembranes 27, 470-490]. Control
coefficients are directly and graphically accessible as the slopes of
log-log graphs, and it makes no sense to me to plot data in linear
space where the slopes usually give no direct indication of the value
of a control coefficient (the few exceptions are obvious, e.g.,
flux-control coefficients in a linear pathway). In fact, experiments
should be designed with data representation in log-log form in mind.
Now to the question of whether our students or fellow biochemists are
too stupid to understand logarithms. I can understand that students
may have a poor mathematical background without much exposure to
logarithms, but as teachers we cannot just pass the buck. If we
believe the concept of logarithm to be important enough, we shouldn't
moan about how terrible their background is, we should get off our
backsides and make it our responsibility to explain what it is and why
it is important. The buck should stop with you. That would mean a next
generation of biochemists that do not sit befuddled when you give a
talk using logarithms.
So, to answer Benno's question of 'Which is the biologically more
correct expression?' my answer is `the logarithmic form'.
Jannie Hofmeyr
