Skip to main content

replacement - How to stop Replace duplicating a list when using Table?


I have a 3 dimensional list of data pairs in the form:


{{{{x11,y11},{x12,y12}},{x1...,y1...}},{{x21,y21},{x22,y22}},{x2...,y2...}}... etc

Incidentally the data originates from a Gas Chromatograph, and is ordered by: [[Channel (1-4), Experiment Number (1 - some number), Peak Number (1 - some number)]], and the pairs represent {Retentiom time, Peak area}.


I want to use the replace function to search the data under the condition that the retention time falls within some range, when this condition is satisfied for the pair: {x_,y_}, x is replaced by the name of the gas that elutes e.g. CH4, C2H4 etc., and y is replaced by the peak area multiplied by a response factor.


The retention time window condition is defined for each channel and for each species. Therefore, I made a list of species and channels containing the time windows, the species name and response factor: e.g.


species={CH4,C2H4,etc...}
CH4={CH4ch1,CH4ch2,CH4ch3,CH4ch4}

CH4ch1={{retentiontimeMin,retentiontimeMax},{"speciesname",responsefactor}}

The code that I am using is as follows:


Table[gcData[[channel, All, All]] /. {x_, y_} /; 
 species[[l, channel, 1, 1]] < x < 
  species[[l, channel, 1, 2]] -> {species[[l, channel, 2, 2]], 
 y*species[[l, channel, 2, 1]]}, {channel, 1, 4}, {l, 1, 7}]

Where gcData is the list of data, and l is the species number.


My problem is that when I use replace I get my original list of data, duplicated 7 times (the number of species I am searching for), where in each iteration the species I am searching for is correctly identified and replace, but on the subsequent iteration I do not see the originally replaced species.



A sample section from the resultant data is shown below:


{{{{"CH4", 34423708},
   {1.581, 240631},
   {1.741, 63594},
   {2.192, 5568}}}
 {{{1.406, 34423708},
   {"C2H6", 0.292896},
   {1.741, 63594},
   {2.192, 5568},}}},
 {{{1.406, 34423708},

   {1.581, 240631},
   {"C2H4", 0.0772031},
   {2.192, 5568},}}}}

How do I stop it duplicating the list?




Comments

Post a Comment

Popular posts from this blog

mathematical optimization - Minimizing using indices, error: Part::pkspec1: The expression cannot be used as a part specification

I want to use Minimize where the variables to minimize are indices pointing into an array. Here a MWE that hopefully shows what my problem is. vars = u@# & /@ Range[3]; cons = Flatten@ { Table[(u[j] != #) & /@ vars[[j + 1 ;; -1]], {j, 1, 3 - 1}], 1 vec1 = {1, 2, 3}; vec2 = {1, 2, 3}; Minimize[{Total@((vec1[[#]] - vec2[[u[#]]])^2 & /@ Range[1, 3]), cons}, vars, Integers] The error I get: Part::pkspec1: The expression u[1] cannot be used as a part specification. >> Answer Ok, it seems that one can get around Mathematica trying to evaluate vec2[[u[1]]] too early by using the function Indexed[vec2,u[1]] . The working MWE would then look like the following: vars = u@# & /@ Range[3]; cons = Flatten@{ Table[(u[j] != #) & /@ vars[[j + 1 ;; -1]], {j, 1, 3 - 1}], 1 vec1 = {1, 2, 3}; vec2 = {1, 2, 3}; NMinimize[ {Total@((vec1[[#]] - Indexed[vec2, u[#]])^2 & /@ R...
Post a Comment
Read more

functions - Get leading series expansion term?

Given a function f[x] , I would like to have a function leadingSeries that returns just the leading term in the series around x=0 . For example: leadingSeries[(1/x + 2)/(4 + 1/x^2 + x)] x and leadingSeries[(1/x + 2 + (1 - 1/x^3)/4)/(4 + x)] -(1/(16 x^3)) Is there such a function in Mathematica? Or maybe one can implement it efficiently? EDIT I finally went with the following implementation, based on Carl Woll 's answer: lds[ex_,x_]:=( (ex/.x->(x+O[x]^2))/.SeriesData[U_,Z_,L_List,Mi_,Ma_,De_]:>SeriesData[U,Z,{L[[1]]},Mi,Mi+1,De]//Quiet//Normal) The advantage is, that this one also properly works with functions whose leading term is a constant: lds[Exp[x],x] 1 Answer Update 1 Updated to eliminate SeriesData and to not return additional terms Perhaps you could use: leadingSeries[expr_, x_] := Normal[expr /. x->(x+O[x]^2) /. a_List :> Take[a, 1]] Then for your examples: leadingSeries[(1/x + 2)/(4 + 1/x^2 + x), x] leadingSeries[Exp[x], x] leadingSeries[(1/x + 2 + (1 - 1/x...
Post a Comment
Read more

What is and isn't a valid variable specification for Manipulate?

I have an expression whose terms have arguments (representing subscripts), like this: myExpr = A[0] + V[1,T] I would like to put it inside a Manipulate to see its value as I move around the parameters. (The goal is eventually to plot it wrt one of the variables inside.) However, Mathematica complains when I set V[1,T] as a manipulated variable: Manipulate[Evaluate[myExpr], {A[0], 0, 1}, {V[1, T], 0, 1}] (*Manipulate::vsform: Manipulate argument {V[1,T],0,1} does not have the correct form for a variable specification. >> *) As a workaround, if I get rid of the symbol T inside the argument, it works fine: Manipulate[ Evaluate[myExpr /. T -> 15], {A[0], 0, 1}, {V[1, 15], 0, 1}] Why this behavior? Can anyone point me to the documentation that says what counts as a valid variable? And is there a way to get Manpiulate to accept an expression with a symbolic argument as a variable? Investigations I've done so far: I tried using variableQ from this answer , but it says V[1...
Post a Comment
Read more