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

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;
%% And Can it be arranged in ascending order (Please help!)
%% vpa(Fv,5)  can not consider all the terms

Have a try!

Answer 1

[Walter Roberson]

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.

[MINATI PATRA]

Dear Walter

I am in 2016b Matlab version where

sympref('PolynomialDisplayStyle', 'ascend')

is not working. (Is there any other command to replace it?)

Second is, I want to change 'Fv' as in the following style (Some terms are not in Exponential form)(Ascending order)

- 4.4574e-25*x^21 + 3.0044e-21*x^20 - 5.6303e-17*x^19 + ...

I need Exponential form (above expression type) and Ascending order.

[Walter Roberson]

format short eng
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 = 

fliplr(sym2poly(Fv))

ans = 1×22

78.4870e-003 784.8700e-003 -2.0757e+000 189.7000e-003 -254.2000e-003 -840.8800e-006 -10.7970e-003 -1.1636e-003 103.9900e-006 -80.6940e-006 21.1290e-006 11.0880e-006 -489.7100e-009 -73.8550e-009 -202.6200e-009 -2.8806e-009 13.6360e-009 -1.4891e-009 173.7900e-015 -56.3030e-018 3.0044e-021 -445.7400e-027

The "long eng" and "short eng" formats are the only ones that automatically format numbers between 1e5 and 1e-5 in exponential format. If you need 2.0757 to show up as 2.0757e+0 then you would need to convert it all into character vector form rather than into numeric or symbolic form.

What is your context that requires that all numbers be expressed in exponential form?

[MINATI PATRA]

Actually I want (Some part taken into consideration)

+ 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

as (1-digit before decimal then exponential form)

+ 1.1088e-5*x^11 + 2.1129e-5*x^10 - 8.0694e-5*x^9 + 1.0399e-4*x^8 - 1.1636e-3*x^7 - 1.0797e-2*x^6 - 8.4088e-4*x^5

[Walter Roberson]

None of the built-in MATLAB display formats will do that for you.

If you were preparing a character vector with the results, then you would have more options.

Do you need the result to be character? Do you need the result to be symbolic? Do you need to write this out to a file? Is this to be displayed in a GUI?

[MINATI PATRA]

Ok

Thanks Walter

I will try then it manually