DifferenceDelta[f,i]
给出离散差分
.
DifferenceDelta[f,{i,n}]
给出多重差分
.
DifferenceDelta[f,{i,n,h}]
给出步长 h 的多重差分.
DifferenceDelta[f,i,j,…]
计算关于 i、j、… 的偏差分.
DifferenceDelta
DifferenceDelta[f,i]
给出离散差分
.
DifferenceDelta[f,{i,n}]
给出多重差分
.
DifferenceDelta[f,{i,n,h}]
给出步长 h 的多重差分.
DifferenceDelta[f,i,j,…]
计算关于 i、j、… 的偏差分.
更多信息和选项
- DifferenceDelta[f,i] 可以输入 if. 字符 通过输入
diffd
或 \[DifferenceDelta]得到. 变量 i 作为下标输入. - 所有没有明确依赖于给定变量的数据量采用零偏差分.
- DifferenceDelta[f,i,j] 可以输入 i,jf. 字符 \[InvisibleComma]通过输入
,
得到,可以用普通的逗号替代. - DifferenceDelta[f,{i,n,h}] 可以输入 { i,n,h }f.
- DifferenceDelta[f,…,Assumptions->assum] 在计算离散差分中,用假定 assum.
范例
打开所有单元 关闭所有单元基本范例 (4)
DifferenceDelta[f[i], i]DifferenceDelta[f[i], {i, 1, h}]DifferenceDelta[Sin[a i + b], {i, 5}]DifferenceDelta[Cosh[a i + b], {i, 2, h}]Subscript[, i]FactorialPower[i, n]DifferenceDelta 是 Sum 的逆运算:
Subscript[, i]Subscript[∑, i]f[i]Subscript[∑, i]Subscript[, i]f[i]范围 (21)
基本用法 (5)
DifferenceDelta[f[i], i]DifferenceDelta[f[i], {i, 2}]DifferenceDelta[f[i], {i, 1, h}]DifferenceDelta[f[i], {i, 2, h}]DifferenceDelta[f[i, j], i, j]DifferenceDelta[f[i, j], {i, 2}, j]DifferenceDelta[f[i, j], {i, 1, r}, {j, 1, s}]DifferenceDelta 线性作用于列表:
DifferenceDelta[{f[i], g[i]}, i]特殊序列 (11)
DifferenceDelta[i ^ 3, i]Table[DifferenceDelta[i ^ 3, {i, n}], {n, 4}]对于离散操作,FactorialPower 比 Power 通常更方便:
DifferenceDelta[FactorialPower[i, 3], i]您可以通过 FunctionExpand 转化一个 Power 表示:
FunctionExpand[FactorialPower[i, 3]]DifferenceDelta 在 FactorialPower 上的 DifferenceDelta 有和 Power 上 D 的相同效果:
DifferenceDelta[FactorialPower[i, n], {i, 3}]D[Power[i, n], {i, 3}]DifferenceDelta[(i + 1) / (i + 3), i]Table[DifferenceDelta[(i + 1) / (i + 3), {i, n}], {n, 2}]有负数幂的 FactorialPower 是有理函数:
FactorialPower[i, -3]//FunctionExpandDifferenceDelta[FactorialPower[i, -3], i]PolyGamma 的差分是有理函数:
Table[DifferenceDelta[PolyGamma[n, i], i], {n, 0, 4}]在离散计算中,PolyGamma 的角色和连续计算中 Log 相似:
Sum[1 / i, i]Integrate[1 / x, x]HarmonicNumber 和 Zeta 也可以产生有理函数的差分:
DifferenceDelta[HarmonicNumber [i, 2], i]DifferenceDelta[Zeta[2, i], i]DifferenceDelta[a ^ i, i]Table[DifferenceDelta[a ^ i, {i, n}], {n, 3}]DifferenceDelta[a ^ i, {i, n}]DifferenceDelta 的二次幂
的角色和 D 的
相同:
DifferenceDelta[2 ^ i, i]D[Exp[x], x]DifferenceDelta[(i ^ 2 + i + 1)2 ^ i, i]Table[DifferenceDelta[(i ^ 2 + i + 1)2 ^ i, {i, n}], {n, 2}]//SimplifyDifferenceDelta[(i + 1) / (i + 3)2 ^ i, i]Table[DifferenceDelta[(i + 1) / (i + 3)2 ^ i, {i, n}], {n, 2}]LerchPhi 的差分乘以指数是有理指数:
DifferenceDelta[λ^iLerchPhi[λ, 2, i], i]Table[DifferenceDelta[λ^iLerchPhi[λ, n, i], i], {n, 2, 5}]DifferenceDelta[Sin[a i + b], i]DifferenceDelta[Sinh[a i + b], i]Table[DifferenceDelta[Sin[a i + b], {i, n}], {n, 2}]DifferenceDelta[Sin[a i + b], {i, n}]DifferenceDelta[Pochhammer[i, n], i]DifferenceDelta[FactorialPower[i, n], i]DifferenceDelta[i!, i]DifferenceDelta[Binomial[i + n, n], i]DifferenceDelta[Gamma[i], i]DifferenceDelta[Beta[i, n], i]一个普通的超几何项由一个有理 DiscreteRatio 的定义:
DiscreteRatio[(FactorialPower[a, i]/FactorialPower[b, i]), i]DifferenceDelta[(FactorialPower[a, i]/FactorialPower[b, i]), i]DifferenceDelta[QFactorial[i, q], i]DifferenceDelta[QGamma[i, q], i]DifferenceDelta[QPochhammer[5, q, i], i]DifferenceDelta[QBinomial[i, m, q], i]DifferenceDelta[QBinomial[n, i, q], i]DifferenceDelta[Fibonacci[i + 5], {i, 2}]DifferenceDelta[LucasL[i + 5], {i, 3}]DifferenceDelta[ChebyshevT[i, x], {i, 3}]DifferenceDelta[BesselJ[i + 2, x], {i, 3}]GammaRegularized 关于 i 的差分是超几何项:
DifferenceDelta[GammaRegularized[i, z], i]相似地有 BetaRegularized:
DifferenceDelta[BetaRegularized[z, i, j], i]DifferenceDelta[BetaRegularized[z, i, j], j]DifferenceDelta[MarcumQ[i, a, z], i]特殊运算 (5)
DifferenceDelta[Sum[f[i], i], i]Sum[DifferenceDelta[f[i], i], i]DifferenceDelta[Sum[f[i, j], i], j]DifferenceDelta[Sum[f[i], {i, j + a, j + b}], j]DifferenceDelta[Product[f[i, j], i], j]DifferenceDelta[Product[f[i], {i, m, n}], m]DifferenceDelta[Product[f[i], {i, m, n}], n]DifferenceDelta[Integrate[f[i], i], i]DifferenceDelta[Integrate[f[i, j], i], j]DifferenceDelta[Integrate[f[i], {i, a, j}], j]DifferenceDelta[Limit[f[i], i -> j], j]DifferenceDelta[Limit[f[i], i -> j], i]应用 (9)
求和方程和差分方程 (3)
Sum[i ^ 2 + i i!, i]DifferenceDelta[%, i]DifferenceDelta[u[i] ^ 2 + E ^ v[i] + w ^ z[i], i]Sum[%, i]用 DifferenceDelta 定义差分方程:
RSolve[DifferenceDelta[u[n], n] + (n + 1) u[n] == 0, u, n]RSolve[ n DifferenceDelta[u[n], {n, 2}] + (n - 2)DifferenceDelta[u[n], {n, 1}] - u[n] == 0, u, n ]其它运算 (3)
对于序列,通过 DifferenceDelta 定义一个符号 Mean 的运算:
DiscreteMean[f_, i_] := Simplify[(-1) ^ (i + 1)DifferenceDelta[(-1) ^ i f, i] / 2, i∈Integers]DiscreteMean[f[i], i]DiscreteMean[i, i]DiscreteMean[Sin[a i + b], i]BackwardDifference[f_, i_] := -DifferenceDelta[f, {i, 1, -1}]BackwardDifference[f[i], i]BackwardDifference[Pochhammer[i, 3], i]BackwardDifference[FactorialPower[i, 3, -1], i]SymmetricDiff[f_, i_] := DiscreteShift[DifferenceDelta[f, i], {i, 1, -1 / 2}]SymmetricDiff[f[i], i]SymmetricDiff[i ^ 3, i]SymmetricDiff[2 ^ i, i]SymmetricDiff[Sum[f[i], i], i]阶乘级数 (2)
FactorialSeries[f_, {x_, x0_, n_, h_ : 1}] := Sum[(DifferenceDelta[f, {x, i, h}] /. x -> x0)FactorialPower[x - x0, i, h] / (h ^ i i!), {i, 0, n}]FactorialSeries[x ^ 2 + x + 1, {x, 0, 3}]FullSimplify[%]级数也是一个 Newton 级数,它通过 InterpolatingPolynomial 计算:
InterpolatingPolynomial[Table[{x, x ^ 2 + x + 1}, {x, 0, 3}], x]Expand[%]FactorialSeries[Sin[x / 5], {x, 0, 2}]FullSimplify[%]Plot[Evaluate@Table[FactorialSeries[Sin[x / 5], {x, 0, n}], {n, 1, 5}], {x, -5Pi, 5Pi}, Ticks -> {{-5Pi, 0, 5Pi}, Automatic}]FactorialSeries[Sin[x / 5], {x, 0, 2}](% /. Table[{x -> i}, {i, 0, 2}]) - Table[Sin[x / 5], {x, 0, 2}]//SimplifyNormal@Series[Sin[x / 5], {x, 1, 2}]Table[D[%, {x, i}], {i, 0, 2}] - Table[D[Sin[x / 5], {x, i}], {i, 0, 2}] /. x -> 1//SimplifyFactorialSeriesCoefficient[f_, {x_, x0_, n_, h_ : 1}] := (DifferenceDelta[f, {x, n, h}] /. x -> x0) / (h ^ n n!)FactorialPower[x,2] 的系数:
FactorialSeriesCoefficient[3x ^ 2 + x + 1, {x, 0, 2}]FactorialSeriesCoefficient[Sin[x / 5], {x, 0, 2}]FactorialPower[x,n] 的系数:
FactorialSeriesCoefficient[Sin[x / 5], {x, 0, n}]FactorialSeriesCoefficient[Exp[x], {x, 0, n}]概率和统计 (1)
可以利用 DifferenceDelta 根据分布的 CDF 计算离散概率分布的 PDF:
cdf = CDF[BernoulliDistribution[p], k]DifferenceDelta[%, k, Assumptions -> Element[k, Integers]]PDF[BernoulliDistribution[p], k + 1]//Simplify属性和关系 (7)
DifferenceDelta 是线性运算:
Subscript[, i](a f[i] + b g[i])Subscript[, i](f[i]g[i])f[i]Subscript[, i]g[i] + Subscript[, i]f[i]Subscript[, i]g[i]Simplify[%% - %]Subscript[, i](f[i]/g[i])(g[i]Subscript[, i]f[i] - f[i]Subscript[, i]g[i]/g[i]Subscript[, i]g[i])Simplify[%% - %]DifferenceDelta 满足一个 Leibniz 的乘积规则:
LeibnizDifference[f_, g_, {i_, n_}] := Underoverscript[∑, k = 0, n]Binomial[n, k](Subscript[, {i, k}]f) (Subscript[, {i, n - k}]Subscript[, {i, k}]g)LeibnizDifference[f[i], g[i], {i, 2}]DifferenceDelta[f[i]g[i], {i, 2}]Simplify[%% - %]DifferenceDelta 是的 Sum 的逆运算:
Subscript[∑, i]Subscript[, i]f[i]Subscript[, i]Subscript[∑, i]f[i]DifferenceDelta 可以按照 DiscreteShift 表示:
DifferenceDeltaShift[f_, {i_, n_}] := Underoverscript[∑, k = 0, n]Binomial[n, k](-1)^n - kSubscript[, {i, k}]fDifferenceDeltaShift[f[i], {i, 2}]DifferenceDelta[f[i], {i, 2}]DiscreteShift 可以按照 DifferenceDelta 表示:
DiscreteShiftDelta[f_, {i_, n_}] := Underoverscript[∑, k = 0, n]Binomial[n, k]Subscript[, {i, k}]fDiscreteShiftDelta[f[i], {i, 2}]DiscreteShift[f[i], {i, 2}]Simplify[%% - %]DifferenceDelta 是 D 的离散模拟:
(1/h)Subscript[, {x, 1, h}]f[x]Limit[%, h -> 0, Analytic -> True](1/h^2)Subscript[, {x, 2, h}]f[x]Limit[%, h -> 0, Analytic -> True]用 Differences 计算列表元素的差分:
Table[Evaluate@DifferenceDelta[f[i], i], {i, 3}]Differences[Table[f[i], {i, 4}]]Table[Evaluate@DifferenceDelta[f[i], {i, 2}], {i, 3}]Differences[Table[f[i], {i, 5}], 2]用 DiscreteRatio 来表示 DifferenceDelta:
DifferenceDelta[y[n], n] == (DiscreteRatio[y[n], n] - 1) y[n]//Simplify文本
Wolfram Research (2008),DifferenceDelta,Wolfram 语言函数,https://reference.wolfram.com/language/ref/DifferenceDelta.html.
CMS
Wolfram 语言. 2008. "DifferenceDelta." Wolfram 语言与系统参考资料中心. Wolfram Research. https://reference.wolfram.com/language/ref/DifferenceDelta.html.
APA
Wolfram 语言. (2008). DifferenceDelta. Wolfram 语言与系统参考资料中心. 追溯自 https://reference.wolfram.com/language/ref/DifferenceDelta.html 年
BibTeX
@misc{reference.wolfram_2026_differencedelta, author="Wolfram Research", title="{DifferenceDelta}", year="2008", howpublished="\url{https://reference.wolfram.com/language/ref/DifferenceDelta.html}", note=[Accessed: 10-September-2026]}
BibLaTeX
@online{reference.wolfram_2026_differencedelta, organization={Wolfram Research}, title={DifferenceDelta}, year={2008}, url={https://reference.wolfram.com/language/ref/DifferenceDelta.html}, note=[Accessed: 10-September-2026]}