DiscreteRatio[f,i]
gives the discrete ratio
.
DiscreteRatio[f,{i,n}]
gives the multiple discrete ratio.
DiscreteRatio[f,{i,n,h}]
gives the multiple discrete ratio with step h.
DiscreteRatio[f,i,j,…]
computes the partial difference ratio with respect to i, j, ….
DiscreteRatio
DiscreteRatio[f,i]
gives the discrete ratio
.
DiscreteRatio[f,{i,n}]
gives the multiple discrete ratio.
DiscreteRatio[f,{i,n,h}]
gives the multiple discrete ratio with step h.
DiscreteRatio[f,i,j,…]
computes the partial difference ratio with respect to i, j, ….
Details and Options
- DiscreteRatio[f,i] can be input as if. The character is entered
dratio
or as \[DiscreteRatio]. The variable i is entered as a subscript. - All quantities that do not explicitly depend on the variables given are taken to have discrete ratio equal to one.
- A multiple discrete ratio is defined recursively in terms of lower discrete ratios.
- Discrete ratio is the inverse operator to indefinite product. »
- DiscreteRatio[f,…,Assumptions->assum] uses the assumptions assum in the course of computing discrete ratios.
Examples
open all close allBasic Examples (4)
Discrete ratio with respect to i:
DiscreteRatio[f[i], i]Discrete ratio for a geometric progression corresponds to the ratio:
DiscreteRatio[r ^ i, i]Enter using
dratio
, and subscripts using
:
Subscript[, i]Pochhammer[x, i]Discrete ratio is the inverse operator to Product:
Subscript[∏, i]Subscript[, i]f[i]Subscript[, i]Subscript[∏, i]f[i]Scope (20)
Basic Use (4)
DiscreteRatio[f[i], i]DiscreteRatio[f[i], {i, 2}]Explicit shift structure in the function will typically be canceled:
DiscreteRatio[f[i]f[i + 1]f[i + 2], i]DiscreteRatio[(f[i]f[i + 1]f[i + 2]/g[i]g[i + 1]), i]Compute the discrete ratio of step h:
DiscreteRatio[f[i], {i, 1, h}]The second discrete ratio of step h:
DiscreteRatio[f[i], {i, 2, h}]Compute the partial discrete ratio:
DiscreteRatio[f[i, j], i, j]DiscreteRatio[f[i, j], i, {j, 2}]DiscreteRatio[f[i, j], i, {j, 2, 1 / 3}]Special Sequences (14)
Polynomials have rational function ratios:
Subscript[, x]x^2The root locations get shifted:
Subscript[, x]((x - Subscript[r, 1])(x - Subscript[r, 2]))Rational functions have rational function ratios:
Subscript[, x](1 + x/1 + x^2)The root and pole locations get shifted:
Subscript[, x](((x - Subscript[r, 1])(x - Subscript[r, 2])/(x - Subscript[p, 1])(x - Subscript[p, 2])))Factorial functions have rational ratios including FactorialPower:
FactorialPower[x, 5]//FunctionExpandDiscreteRatio[%, x]DiscreteRatio[FactorialPower[a, x], x]Pochhammer[x, 5]DiscreteRatio[%, x]DiscreteRatio[Pochhammer[a, x], x]DiscreteRatio[Factorial[x], x]DiscreteRatio[Gamma[x], x]DiscreteRatio[Binomial[x, k], x]DiscreteRatio[Binomial[n, x], x]Exponential sequences have constant ratios:
DiscreteRatio[r^x, x]The ratio of an exponential sequence corresponds to the DifferenceDelta of the exponent:
Subscript[, x]r^f[x]r^Subscript[, x]f[x]Hypergeometric terms are products of factorial, rational, and exponential functions:
DiscreteRatio[(FactorialPower[x, Subscript[a, 1]]Binomial[x, Subscript[a, 2]]/Pochhammer[x, Subscript[b, 1]]Factorial[x])r^x, x]Hypergeometric terms have rational ratios, so CatalanNumber is a hypergeometric term:
DiscreteRatio[CatalanNumber[x], x]FunctionExpand[CatalanNumber[x]]Q-polynomials (polynomials of exponentials) have q-rational ratios:
DiscreteRatio[a q ^ x + b q ^ (2x), x]The roots are shifted in a geometric fashion:
DiscreteRatio[(q^x - Subscript[r, 1])(q^x - Subscript[r, 2]), x]Q-rational functions (rational functions of exponentials) have q-rational ratios:
DiscreteRatio[(a q ^ x + b q ^ (2x)/1 + q^x), x]The roots and poles are shifted in a geometric fashion:
DiscreteRatio[((q^x - Subscript[r, 1])(q^x - Subscript[r, 2])/(q^x - Subscript[p, 1])(q^x - Subscript[p, 2])), x]Q-factorial functions have q-rational ratios including QPochhammer:
QPochhammer[x, q, 5]//FunctionExpandDiscreteRatio[%, x]DiscreteRatio[QPochhammer[a, q, x], x]DiscreteRatio[QFactorial[x, q], x]DiscreteRatio[QBinomial[n, x, q], x]DiscreteRatio[QBinomial[x, k, q], x]Q-hypergeometric terms are defined by having a q-rational discrete ratio:
DiscreteRatio[(QBinomial[a, x, q]QFactorial[x, q]/QPochhammer[b, q, x]), x]Products of factorial functions have factorial ratios, including BarnesG:
DiscreteRatio[BarnesG[x], x]Then the second ratio is rational:
DiscreteRatio[%, x]Hyperfactorial is a product of ii:
DiscreteRatio[Hyperfactorial[x], x]A multivariate hypergeometric term is hypergeometric in each variable:
{DiscreteRatio[Binomial[n, k], n], DiscreteRatio[Binomial[n, k], k]}The binomial distribution is a multivariate hypergeometric term:
f = Refine[PDF[BinomialDistribution[n, p], k], 0 ≤ k < n]{DiscreteRatio[f, n], DiscreteRatio[f, k]}The difference of GammaRegularized with respect to
is a hypergeometric term:
DifferenceDelta[GammaRegularized[n, z], n]This gives a simple expression for the ratio:
1 + % / GammaRegularized[n, z]DiscreteRatio[GammaRegularized[n, z], n]Similarly for BetaRegularized:
DiscreteRatio[BetaRegularized[z, n, m], m]The difference for MarcumQ is expressed in terms of BesselI:
DifferenceDelta[MarcumQ[n, a, z], n]Special Operators (2)
DiscreteRatio is the inverse operator to Product:
DiscreteRatio[Product[f[i], i], i]Product[DiscreteRatio[f[i], i], i]DiscreteRatio[Product[f[k], {k, i + m, i + p}], i]DiscreteRatio[Product[f[i, j], i, j], i, j]DiscreteRatio[Limit[f[x], x -> a], a]DiscreteRatio[Integrate[f[x], x], x]DiscreteRatio[Sum[f[k], k], k]In this case the variable x is scoped:
DiscreteRatio[Integrate[f[x], {x, a, b}], x]DiscreteRatio[Limit[f[x], x -> a], x]Applications (6)
The defining property for a geometric sequence is that its DiscreteRatio is constant:
DiscreteRatio[c^a k + b, k]Solve a compound interest problem with interest rate 1+r:
RSolve[y[k + 1] == (1 + r) y[k], y[k], k]DiscreteRatio gives the interest rate the compounding sequence:
DiscreteRatio[y[k] /. First[%], k]The frequencies used in an even-tempered scale form a geometric progression with ratio
:
DiscreteRatio[(2^(1/(12)))^i440 , i]Synthesize tones directly from frequencies:
f = Piecewise@Table[{(2^(1/(12)))^i440 2Pi t, i ≤ t < i + 1}, {i, 0, 11}];Play[Sin[f], {t, 0, 12}]Sound[Table[SoundNote[i], {i, 0, 11}]]Use the ratio test to verify convergence of a series whose general term is given by:
a[i_] := E ^ (-i)(3i + 1)! / (4i)!Compute the DiscreteRatio for this series:
rat = DiscreteRatio[a[i], i]The series converges since the limit at infinity of the ratio is less than 1:
Limit[rat, i -> ∞]Verify the result using SumConvergence:
SumConvergence[a[i], i]Verify the answer for an indefinite product:
Product[(i + 1) / (2i + 5), i]The DiscreteRatio of a product is equivalent to the factor:
DiscreteRatio[%, i]Verify the solution from RSolve using a higher-step shift ratio:
RSolve[{y[k + 2] == ((k + 1)y[k]) / (k + 2), y[0] == 1, y[1] == 2}, y, k]DiscreteRatio[y[k] /. %[[1]], {k, 1, 2}]//FullSimplifyProperties & Relations (6)
DiscreteRatio is the inverse for indefinite Product:
DiscreteRatio[Product[f[k], k], k]Product[DiscreteRatio[f[k], k], k]DiscreteRatio distributes over products and integer powers:
{DiscreteRatio[f[k] g[k], k], DiscreteRatio[f[k] g[k], k]}{DiscreteRatio[f[k]^3, k], DiscreteRatio[f[k], k]^3}DiscreteRatio is closely related to DifferenceDelta:
{Log[DiscreteRatio[f[k], k]], DifferenceDelta[Log[f[k]], k]}{DiscreteRatio[Exp[f[k]], k], Exp[DifferenceDelta[f[k], k]]}DiscreteRatio can be expressed in terms of DifferenceDelta:
r[n] = DiscreteRatio[y[n], n];
d[n] = DifferenceDelta[y[n], n];r[n] == 1 + d[n] / y[n]//SimplifyUse Ratios to compute ratios of adjacent terms:
Ratios[Table[f[k], {k, 4}]]Table[Evaluate@DiscreteRatio[f[k], k], {k, 3}]Ratios[Table[f[k], {k, 4}], 2]Table[Evaluate@DiscreteRatio[f[k], {k, 2}], {k, 2}]Ratios[Table[f[k], {k, 4}], 1, 2]Table[Evaluate@DiscreteRatio[f[k], {k, 1, 2}], {k, 2}]Use PowerRange to generate a list with constant ratio:
PowerRange[1, 8, 2]Ratios[%]This is the sequence 2k with constant ratio:
DiscreteRatio[2 ^ k, k]Neat Examples (2)
Create a gallery of discrete ratios:
flist = {f[k], Product[f[k], k], a ^ k, k!, CatalanNumber[k], BarnesG[k], QFactorial[k, q]};Grid[Join[{{f[k], Text["Discrete Ratio"]}}, Transpose[{flist, Map[DiscreteRatio[#, k]&, flist]}]], IconizedObject[«Grid options»]]//TraditionalFormSee Also
Ratios Product DifferenceDelta DiscreteShift DifferenceQuotient Pochhammer FactorialPower BarnesG Divide
Characters: \[DiscreteRatio]
Related Guides
History
Text
Wolfram Research (2008), DiscreteRatio, Wolfram Language function, https://reference.wolfram.com/language/ref/DiscreteRatio.html.
CMS
Wolfram Language. 2008. "DiscreteRatio." Wolfram Language & System Documentation Center. Wolfram Research. https://reference.wolfram.com/language/ref/DiscreteRatio.html.
APA
Wolfram Language. (2008). DiscreteRatio. Wolfram Language & System Documentation Center. Retrieved from https://reference.wolfram.com/language/ref/DiscreteRatio.html
BibTeX
@misc{reference.wolfram_2026_discreteratio, author="Wolfram Research", title="{DiscreteRatio}", year="2008", howpublished="\url{https://reference.wolfram.com/language/ref/DiscreteRatio.html}", note=[Accessed: 12-June-2026]}
BibLaTeX
@online{reference.wolfram_2026_discreteratio, organization={Wolfram Research}, title={DiscreteRatio}, year={2008}, url={https://reference.wolfram.com/language/ref/DiscreteRatio.html}, note=[Accessed: 12-June-2026]}