[R] How to do ANOVA with fractional values and overcome the

[(Ted Harding)]

On 06-Sep-07 06:55:36, Emre Sevinc wrote:
> I have exported a CSV file from my EXCEL worksheet and its last column
> contained decimal values:
> 
> Subject;Group;Side;Difference;PercentError
> M3;1;1;;
> M5;1;1;375;18,75
> M8;1;1;250;14,58
> M10;1;1;500;12,50
> M12;1;1;375;25,00
> .
> .
> .
> 
> 
> When I tried to do ANOVA test on it, R complained by givin error:
> 
>> Anova3LongAuditoryFemaleError.data <- read.csv("C:\\Documents\ and\
>> Settings\\Administrator\\My
>> Documents\\CogSci\\tez\\Anova3LongAuditoryFemaleError.csv", header =
>> TRUE, sep = ";")

Perhaps you need to specify the "dec" option to read.csv():

     read.csv(file, header = TRUE, sep = ",", quote="\"", dec=".",
              fill = TRUE, ...)

i.e.

Anova3LongAuditoryFemaleError.data <- read.csv("C:\\Documents\ and\
Settings\\Administrator\\My
Documents\\CogSci\\tez\\Anova3LongAuditoryFemaleError.csv",
header = TRUE, sep = ";", dec=",")

Or else use read.csv2(), where dec = "," is the default. See

  ?read.csv

and read about both read.csv and read.csv2

Otherwise, "18,75" is likely to be treated as text, and not as
a numerical value, and so PercetError will be converted into
a factor with character-valued levels.

Ted.

> 
>> Anova3LongAuditoryFemaleError.aov = aov(PercentError ~ (Group * Side),
>> data = Anova3LongAuditoryFemaleError.data)
> 
> Error in `storage.mode<-`(`*tmp*`, value = "double") : 
>         invalid to change the storage mode of a factor
> In addition: Warning message:
> using type="numeric" with a factor response will be ignored in:
> model.response(mf, "numeric")
> 
> What must I do in order to make the ANOVA test on these fractional
> data?
> 
> Regards.
> 
> --
> Emre Sevinc
> 
>       [[alternative HTML version deleted]]
> 
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E-Mail: (Ted Harding) <Ted.Harding at manchester.ac.uk>
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Date: 06-Sep-07                                       Time: 09:39:04
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