[R] ANOVA in R
Jim Lemon
drj|m|emon @end|ng |rom gm@||@com
Thu Oct 11 00:02:48 CEST 2018
Hi Tranh,
I'm not sure why you are converting your variables to factors, and I
think the model you want is:
lm(KIC~temperature+AC+AV+Thickness+temperature:AC+
temperature:AV+temperature:thickness+AC:AV+
AC:thickness+AV:thickness,SR)
Note the colons (:) rather than asterisks (*) for the interactions.
Jim
On Wed, Oct 10, 2018 at 5:14 PM Thanh Tran <masternhattt using gmail.com> wrote:
>
> Hi eveyone,
> I'm studying about variance (ANOVA) in R and have some questions to share.
> I read an article investigating the effect of factors (temperature, Asphalt
> content, Air voids, and sample thickness) on the hardness of asphalt
> concrete in the tensile test (abbreviated as Kic). Each condition was
> repeated four times (4 samples). In the paper, the authors used MINITAB to
> analyze Anova. The authors use "adjusted sums of squares" calculate the
> p-value I try to use ANOVA in R to analyze this data and get the result as
> shown in Figure 4. The results are different from the results in the
> article. Some papers say that in R, the default for ANOVA analysis is to
> use "sequential sums of squares" to calculate the p-value.
> So please help the following two questions: 1 / Introduction to code in R
> for anova analysis uses "adjusted sums of squares". The main part of the
> command in R / myself is as follows: > Tem = as.factor (temperature) > Ac =
> as.factor (AC) > Av = as.factor (AV) > Thick = as.factor (Thickness) >
> Twoway = lm (KIC ~ Tem + Ac + Av + Thick + Stamp + Ac + Stamp + Av + Stamp
> + Thick + Ac * Av + Ac * Thick + Av * Thick) > anova (twoway) 2/ When to
> use "sequential sums of squares" and when to use "adjusted sums of
> squares". Some papers recommend using the "oa.design
> <https://www.youtube.com/redirect?q=http%3A%2F%2Foa.design%2F&redir_token=AaSAPDY-5UAsoHxN6BdwfyIJ7R98MTUzOTIxNDg2OUAxNTM5MTI4NDY5&event=comments>"
> function in R to check for "orthogonal" designs. If not, use "adjusted sums
> of squares". I am still vague about this command, so look forward to
> everyone's suggestion. If you could answer all two of my questions, I would
> be most grateful. Ps: I have added a CSV file and the paper for practicing
> R. http://www.mediafire.com/file/e5oe54p2c2wd4bc/Saha+research.csv
> http://www.mediafire.com/file/39jlf9h539y9mdz/Homothetic+behaviour+investigation+on+fracture+toughness+of+asphalt+mixtures+using+semicircular+bending+test.pdf
>
> [[alternative HTML version deleted]]
>
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