Linear Regression one variable not showing in results

[Pablo123]

Hi, I'm trying to do a linear regression using the lm() function.

But when I run the lm() function one of the variables isn't showing in the results.
I clean the file for NA's.
The Position column/variable consists of 4 values, "Addition", "Continuation", "Deletion" and "Control"
The columns are Delta.Market.Value (is numeric) and Position (is character)

The codes I use are:

library("readxl")
read_excel("Testfile.xlsx")

Testfile <- read_excel("Testfile.xlsx")

#Import Variables
Position = Testfile$Position
Delta.Market.Value = Testfile$Delta.Market.Value

#Clean file from NA's
Testfile.clean<-na.omit(Testfile)
nrow(Testfile.clean)

#Apoint variables to new data
Position = Testfile.clean$Position
Delta.Market.Value = Testfile.clean$Delta.Market.Value

#Make linear regression
model1<- lm(formula = Delta.Market.Value ~ Position)
summary(model1)

Call:
lm(formula = Delta.Market.Value ~ Position)

The results that I get are the following, as you can see there is no Positionaddition:

Residuals:
Min 1Q Median 3Q Max
-0.92923 -0.15627 -0.01523 0.15411 1.07077

Coefficients:
Estimate Std. Error t value Pr(>|t|)
(Intercept) 0.01531 0.03642 0.421 0.6744
Positioncontinuation 0.00241 0.04637 0.052 0.9586
Positioncontrol -0.08609 0.04912 -1.753 0.0807 .
Positiondeletion -0.07042 0.04928 -1.429 0.1541

Signif. codes: 0 ‘’ 0.001 ‘’ 0.01 ‘’ 0.05 ‘.’ 0.1 ‘ ’ 1

Residual standard error: 0.2797 on 293 degrees of freedom
Multiple R-squared: 0.02055, Adjusted R-squared: 0.01053
F-statistic: 2.05 on 3 and 293 DF, p-value: 0.1071

Does anybody know how I can get the "Addition" from column "Position" as well in the results?

[nutterb]

The Addition level of your categorical factor is being used as a reference level.

• Continuation is 0.00241 units higher than Addition
• Control is 0.08609 units lower than Addition
• Deletion is 0.07042 units lower than Addition

I believe this is fairly standard presentation for linear model results