# Implementing a function to determine the standard error?

Posted 2 months ago
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 Basically, my task is in the question. I need to find out the standard error and I've actually written the code like I imagine it should be. I'll attach a screenshot indicating the output. It should not be this way. Where have I made mistakes?The code: In[136]:= Needs["ErrorBarPlots"] standardError[val_] := StandardDeviation[val]/Sqrt[val["PathLength"]] In[33]:= coeficientOfVariation[val_] := StandardDeviation[val]/Mean[val["PathLength"]] In[13]:= errorBar[type_: "GlassRectangle"][{{x0_, x1_}, {y0_, y1_}}, value_, meta_] := Block[{error, mags = QuantityMagnitude[value]}, error = Flatten[QuantityMagnitude[meta]]; error = If[error === {}, 0, Last[error]]; {ChartElementData[type][{{x0, x1}, {y0, y1}}, mags, meta], {Black, Line[{{{(x0 + x1)/2, y1 - error}, {(x0 + x1)/2, y1 + error}}, {{1/4 (3 x0 + x1), y1 + error}, {1/4 (x0 + 3 x1), y1 + error}}, {{1/4 (3 x0 + x1), y1 - error}, {1/4 (x0 + 3 x1), y1 - error}}}]}}] In[7]:= RadM = {7.3, 6.8, 8.2} RadH = {6.1, 9.4, 11} RadR = {7.4, 5.9, 4.9} RadB = {13.8} In[28]:= stdErr = standardError[RadM] Out[28]= standardError[{7.3, 6.8, 8.2}] In[29]:= varCoef = coefficientOfVariation[RadM] Out[29]= coefficientOfVariation[{7.3, 6.8, 8.2}] Here's the resulting graph:
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Posted 2 months ago
 Out[28] and Out[29] have not evaluated standardError and coefficientOfVariation which means those functions have not been defined. Did you evaluate the cells that contain the definition?
Posted 2 months ago
 The functions standardError and coefficientOfVariation were evaluated.
Posted 2 months ago
 You have a few errors in the code. The definition of coeficientOfVariation[val_] is missing an additional f. Sqrt[val["PathLength"]] should be Sqrt[Length[val]]. Mean[val["PathLength"]] should be Mean[val].
Posted 2 months ago
 One way to include error bars in BarChart is with Around: standardError[val_] := StandardDeviation[val]/Sqrt[Length[val]] LRed = {7.43, 8.83, 6.06, 13.8}; stdErr = standardError[LRed]; LRedAround = Map[Around[#, stdErr] &, LRed]; BarChart[LRedAround, ChartElementFunction -> "GlassRectangle", ChartStyle -> "Pastel"] which gives:
Posted 2 months ago
 The lines indicating the error are not the same as the error. The errors have different values while the lines are all the same.
 It is not so obvious what your data are:)Lets say you have computed your mean data and errors to be: mean = {7.43, 8.83, 6.06, 13.8}; errors = {4, 3, 2, 1}; then you wrap Around to your data: data = Apply[Around, Transpose[{mean, errors}], 1]; and BarChart it: BarChart[data, ChartElementFunction -> "GlassRectangle", ChartStyle -> "Pastel"] which gives:
 Thank you for your help. Unfortunately, I need just a bit more. This section's been giving me a few errors. I made a few changes and it seemed to go well but after saving and restarting, they're back. standardError[val_] := StandardDeviation[val]/Sqrt[Length[val]] LRad = {7.43, 10.1, 6.07, 9.65}; stdErr = standardError[LRad]; LRad = Apply[Around, Transpose[{LRad, stdErr}], 1]; BarChart[LRad, ChartElementFunction -> "GlassRectangle", ChartStyle -> "Pastel", ImageSize -> 500, ChartLabels -> {"1", "2", "3", "4" }, LabelStyle -> {16, Bold}, AxesLabel -> {"", "cm"}, BarSpacing -> 0.3, LabelingFunction -> Bottom] `The errors: