# vpa(Fv,5) can not consider all the terms

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MINATI PATRA 2021 年 6 月 5 日
コメント済み: MINATI PATRA 2021 年 6 月 6 日
Fv = - 4.4574e-25*x^21 + 3.0044e-21*x^20 - 5.6303e-17*x^19 + 1.7379e-13*x^18 - 1.4891e-9*x^17 + 1.3636e-8*x^16 - 2.8806e-9*x^15 - 2.0262e-7*x^14 - 7.3855e-8*x^13 - 4.8971e-7*x^12 + 0.000011088*x^11 + 0.000021129*x^10 - 0.000080694*x^9 + 0.00010399*x^8 - 0.0011636*x^7 - 0.010797*x^6 - 0.00084088*x^5 - 0.2542*x^4 + 0.1897*x^3 - 2.0757*x^2 + 0.78487*x + 0.078487;
%% vpa(Fv,5) can not consider all the terms
Have a try!

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### 採用された回答

Walter Roberson 2021 年 6 月 5 日
It is not clear what you mean about considering all of the terms. vpa(Fv,5) looked fine to me. I did notice, though, that vpa() rounds to that number of significant digits, and perhaps what you want is to round in absolute digits.
sympref('PolynomialDisplayStyle', 'ascend')
ans = 'default'
syms x
Fv = - 4.4574e-25*x^21 + 3.0044e-21*x^20 - 5.6303e-17*x^19 + 1.7379e-13*x^18 - 1.4891e-9*x^17 + 1.3636e-8*x^16 - 2.8806e-9*x^15 - 2.0262e-7*x^14 - 7.3855e-8*x^13 - 4.8971e-7*x^12 + 0.000011088*x^11 + 0.000021129*x^10 - 0.000080694*x^9 + 0.00010399*x^8 - 0.0011636*x^7 - 0.010797*x^6 - 0.00084088*x^5 - 0.2542*x^4 + 0.1897*x^3 - 2.0757*x^2 + 0.78487*x + 0.078487
Fv = mapSymType(Fv, 'rational', @(e)round(e,5))
ans = Is that what you were talking about?
Notice that a lot of the high-order terms are now missing, because their coefficient rounded to 5 decimal places was 0.
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MINATI PATRA 2021 年 6 月 6 日
Ok
Thanks Walter
I will try then it manually

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