How to do Taylor expansions generally for multivariate functions?












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Ok so I have a function like this: $$f(t + 1, z_t + x_t)$$ where $x_t$ equals $z_{t+1} - z_t$.



I want to Taylor-expand this function so that I can get a first-order approximation. How do I do this? I want to expand around $x_t = 0$.



$z_t$ and $x_t$ are random variables, known at time $t$ and $t+1$ respectively, but just treat them as regular variables.










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  • So it's more likely that I get an answer if I make my question less clear and to-the-point by cluttering it with my own messy and incorrect attempts? Yeah, that makes a lot of sense.
    – JohnDoe
    Nov 24 at 12:11










  • $$ f(t + 1, z_t) + left.frac{partial f}{partial x_t}right|_{x_t = 0} x_t + frac{1}{2}left.frac{partial^2 f}{partial x_t^2}right|_{x_t = 0} x_t^2 + cdots $$
    – caverac
    Nov 24 at 12:33










  • check this
    – Masacroso
    Nov 24 at 13:04
















0














Ok so I have a function like this: $$f(t + 1, z_t + x_t)$$ where $x_t$ equals $z_{t+1} - z_t$.



I want to Taylor-expand this function so that I can get a first-order approximation. How do I do this? I want to expand around $x_t = 0$.



$z_t$ and $x_t$ are random variables, known at time $t$ and $t+1$ respectively, but just treat them as regular variables.










share|cite|improve this question






















  • So it's more likely that I get an answer if I make my question less clear and to-the-point by cluttering it with my own messy and incorrect attempts? Yeah, that makes a lot of sense.
    – JohnDoe
    Nov 24 at 12:11










  • $$ f(t + 1, z_t) + left.frac{partial f}{partial x_t}right|_{x_t = 0} x_t + frac{1}{2}left.frac{partial^2 f}{partial x_t^2}right|_{x_t = 0} x_t^2 + cdots $$
    – caverac
    Nov 24 at 12:33










  • check this
    – Masacroso
    Nov 24 at 13:04














0












0








0







Ok so I have a function like this: $$f(t + 1, z_t + x_t)$$ where $x_t$ equals $z_{t+1} - z_t$.



I want to Taylor-expand this function so that I can get a first-order approximation. How do I do this? I want to expand around $x_t = 0$.



$z_t$ and $x_t$ are random variables, known at time $t$ and $t+1$ respectively, but just treat them as regular variables.










share|cite|improve this question













Ok so I have a function like this: $$f(t + 1, z_t + x_t)$$ where $x_t$ equals $z_{t+1} - z_t$.



I want to Taylor-expand this function so that I can get a first-order approximation. How do I do this? I want to expand around $x_t = 0$.



$z_t$ and $x_t$ are random variables, known at time $t$ and $t+1$ respectively, but just treat them as regular variables.







taylor-expansion






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share|cite|improve this question











share|cite|improve this question




share|cite|improve this question










asked Nov 24 at 11:42









JohnDoe

1




1












  • So it's more likely that I get an answer if I make my question less clear and to-the-point by cluttering it with my own messy and incorrect attempts? Yeah, that makes a lot of sense.
    – JohnDoe
    Nov 24 at 12:11










  • $$ f(t + 1, z_t) + left.frac{partial f}{partial x_t}right|_{x_t = 0} x_t + frac{1}{2}left.frac{partial^2 f}{partial x_t^2}right|_{x_t = 0} x_t^2 + cdots $$
    – caverac
    Nov 24 at 12:33










  • check this
    – Masacroso
    Nov 24 at 13:04


















  • So it's more likely that I get an answer if I make my question less clear and to-the-point by cluttering it with my own messy and incorrect attempts? Yeah, that makes a lot of sense.
    – JohnDoe
    Nov 24 at 12:11










  • $$ f(t + 1, z_t) + left.frac{partial f}{partial x_t}right|_{x_t = 0} x_t + frac{1}{2}left.frac{partial^2 f}{partial x_t^2}right|_{x_t = 0} x_t^2 + cdots $$
    – caverac
    Nov 24 at 12:33










  • check this
    – Masacroso
    Nov 24 at 13:04
















So it's more likely that I get an answer if I make my question less clear and to-the-point by cluttering it with my own messy and incorrect attempts? Yeah, that makes a lot of sense.
– JohnDoe
Nov 24 at 12:11




So it's more likely that I get an answer if I make my question less clear and to-the-point by cluttering it with my own messy and incorrect attempts? Yeah, that makes a lot of sense.
– JohnDoe
Nov 24 at 12:11












$$ f(t + 1, z_t) + left.frac{partial f}{partial x_t}right|_{x_t = 0} x_t + frac{1}{2}left.frac{partial^2 f}{partial x_t^2}right|_{x_t = 0} x_t^2 + cdots $$
– caverac
Nov 24 at 12:33




$$ f(t + 1, z_t) + left.frac{partial f}{partial x_t}right|_{x_t = 0} x_t + frac{1}{2}left.frac{partial^2 f}{partial x_t^2}right|_{x_t = 0} x_t^2 + cdots $$
– caverac
Nov 24 at 12:33












check this
– Masacroso
Nov 24 at 13:04




check this
– Masacroso
Nov 24 at 13:04















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