Error: invalid type(list) for variable when using lm()

On Nov 25, 2011, at 11:41 AM, Dhaynes wrote:

Ok let me clarify

I have multidimensional array and I need to convert it to a singular
dimensional array.
The multidimensional array is 359 rows, 2 cols, 3 deep
I need to run a regression model mymatrix[1,1,1:3] and mymatrix [1,2,1:3]

This is my current error, which indicates I have the incorrect list type
(I
have tried functions as.list, as.vector, as.vector)

lm(formula = mymatrix[1,1,1:3]~mymatrix[1,2,1:3] )
Error in model.frame.default(formula = mymatrix[1, 1, 1:3] ~ mymatrix[1,
?:
?invalid type (list) for variable 'mymatrix[1, 1, 1:3]'


I was unsuccessful at attempting the "str(mymatrix[1,1,1:3]" --Argument
not
valid model

The data.frame function did not create the objects
<- data.frame(a=mymatrix[1,1,1:3], b=mymatrix[1,2,1:3])

lm(a~b, data=df)

Error in eval(expr, envir, enclos) : object 'a' not found

Here is my code
con <- dbConnect(PostgreSQL(), user="postgres",
password="antione",dbname="Education")
rs <- dbGetQuery(con, "SELECT (GRADE1[10]) As grade1_t1, (GRADE1[11]) As
grade1_t2, (GRADE1[12]) As grade1_t3, (GRADE2[11]) As grade2_t2,
(GRADE2[12]) As grade2_t3, (GRADE2[13]) As grade2_t4 FROM attending")

myval <- rs
attach(myval)

Generally a bad idea to attach objects. It's a sin that is committed by
several authors but it generally gets in the way of safe code writing.
Better to use with().

names(myval)
dim(myval)

mymatrix <- array(myval, c(379,2,3))

mymatrix[,1,1] <- grade1_t1
mymatrix[,1,2] <- grade1_t2
mymatrix[,1,3] <- grade1_t3
mymatrix[,2,1] <- grade2_t2
mymatrix[,2,2] <- grade2_t3
mymatrix[,2,3] <- grade2_t4

But what are these various grade-named objects? Are you sure you didn't
coerce the matrix to character mode? What is str(mymatrix) after this?


--
David.

I can do this
plot(mymatrix[1,1,1:3],mymatrix[1,2,1:3])

On Fri, Nov 25, 2011 at 6:06 AM, Bert Gunter [via R] <
ml-node+s789695n4107159h96 at n4.nabble.com> wrote:

Inline below.

-- Bert

On Fri, Nov 25, 2011 at 2:31 AM, Milan Bouchet-Valat <[hidden
email]<http://user/SendEmail.jtp?type=node&node=4107159&i=0>>
wrote:

Le vendredi 25 novembre 2011 ? 00:02 -0800, Dhaynes a ?crit :

Hello,

I am new to R.
I have multidimensional array (379,2,3) and I need to create a series

of

linear regressions (379 to be exact)
I have the array stored properly I believe, but I can not use the
lm(myarray[1,1,1:3]~myarray[1,2,1:3])
I have checked to make sure they are exactly the same length.
I have also tried endlessly to convert the subset of the array back

into a

vector.

?as.vector
Actually an array **is** a vector -- but with an additional "dim"
attribute. Try:

str(x)

any help would be appreciated.

1) Read relevant portions of R docs, like ?array and perhaps "An
Introduction to R."

2) ?Read and follow the posting guide. In particular, give us a toy
example with the code you used to construct your array. It's difficult
to diagnose the source of engine failure without the car.

3) See my comment below.

The 'formula' argument of lm doesn't take actual values, but variable
names. So you need to create vectors containing your data, or pass a

--This is patently false. Please check before giving obviously wrong
advice:

x <- array(rnorm(150), dim= c(10,5,3))
lm(x[,3,2] ~x[,1,1])

Call:
lm(formula = x[, 3, 2] ~ x[, 1, 1])

Coefficients:
(Intercept) ? ?x[, 1, 1]
? -0.1247 ? ? ? 0.1171

data frame with these vectors are columns. So, going the latter way :
df <- data.frame(a=myarray[1,1,1:3], b=myarray[1,2,1:3])
lm(a ~ b, data=df)

or in one step
lm(a ~ b, data=data.frame(a=myarray[1,1,1:3], b=myarray[1,2,1:3]))


Regards

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David Winsemius, MD
West Hartford, CT