stansummary save to CSV doesn't respect default significant figures

[mitzimorris]

Summary:

Utility stansummary use of sig figs combined with scientific notation results in only 2 digit's worth of precision.

Description:

cf: stan-dev/cmdstanpy#550 (comment)

It seems that the CSV output doesn't respect the default sig-figs that the docs cite.

without specifying -s:

name,Mean,MCSE,StdDev,5%,50%,95%,N_Eff,N_Eff/s,R_hat
"lp__",-7.29137,0.0194958,0.751762,-8.82028,-6.99659,-6.74977,1486.9,19062.8,0.999907
with -s 2

name,Mean,MCSE,StdDev,5%,50%,95%,N_Eff,N_Eff/s,R_hat
"lp__",-7.3,0.019,0.75,-8.8,-7,-6.7,1.5e+03,1.9e+04,1
I should note that the values displayed in stdout do seem to have a default value of 2 significant figures.

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Current Output:

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Expected Output:

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Additional Information:

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Current Version:

v2.29.2

[WardBrian]

I think 6 is actually a better default value, but the issue is it is not documented. More discussion here:
https://discourse.mc-stan.org/t/cmdstanpy-error-in-fit-summary/26939/13?u=wardbrian

Furthermore, as is pointed out earlier in that thread, std::setprecision does not really align with the natural notion of 'significant figures'