R help - Sep 2007 - How to do ANOVA with fractional values and overcome the error: Error in `storage.mode<-`(`*tmp*`, value = "double") : invalid to change the storage mode of a factor

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 = ";")
> 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]]

Your data file has commas as the decimal point. Use read.csv2 for such 
files.

What happened was that PercentError was read as a factor, and you can't do 
ANOVA on factors.  The warning
> In addition: Warning message:
> using type="numeric" with a factor response will be ignored in:
> model.response(mf, "numeric")
told you and us this quite explicitly.  If you get an error, also look at 
the warnings which may well (as here) tell you what precipitated the 
error.

On Thu, 6 Sep 2007, 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 = ";")
>
>> 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]]
>
> ______________________________________________
> R-help at stat.math.ethz.ch mailing list
> https://stat.ethz.ch/mailman/listinfo/r-help
> PLEASE do read the posting guide
http://www.R-project.org/posting-guide.html
> and provide commented, minimal, self-contained, reproducible code.
>
-- 
Brian D. Ripley,                  ripley at stats.ox.ac.uk
Professor of Applied Statistics,  http://www.stats.ox.ac.uk/~ripley/
University of Oxford,             Tel:  +44 1865 272861 (self)
1 South Parks Road,                     +44 1865 272866 (PA)
Oxford OX1 3TG, UK                Fax:  +44 1865 272595

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]]
> 
> ______________________________________________
> R-help at stat.math.ethz.ch mailing list
> https://stat.ethz.ch/mailman/listinfo/r-help
> PLEASE do read the posting guide
> http://www.R-project.org/posting-guide.html
> and provide commented, minimal, self-contained, reproducible code.
--------------------------------------------------------------------
E-Mail: (Ted Harding) <Ted.Harding at manchester.ac.uk>
Fax-to-email: +44 (0)870 094 0861
Date: 06-Sep-07                                       Time: 09:39:04
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