Why does using paste in for loop return error?

Question

I have a few problems concerning the same topic.

(1) I am trying to loop over:

premium1999 <- as.data.frame(coef(summary(data1999_mod))[c(19:44), 1])

for 10 years, in which I wrote:

for (year in seq(1999,2008)) { 
    paste0('premium',year) <- as.data.frame(coef(summary(paste0('data',year,'_mod')))[c(19:44), 1])
}

Note: for data1999_mod is regression results that I want extract some of its estimators as a dataframe vector. The coef(summary(data1999_mod)) looks like this:

#A matrix: ... of type dbl
             Estimate        Std. Error     t value    Pr(>|t|)
    age      0.0388573570  2.196772e-03   17.6883885  3.362887e-6
    age_sqr -0.0003065876  2.790296e-05  -10.9876373  5.826926e-28
    relation 0.0724525759  9.168118e-03    7.9026659  2.950318e-15
    sex     -0.1348453659  8.970138e-03  -15.0326966  1.201003e-50
    marital  0.0782049161  8.928773e-03    8.7587533  2.217825e-18
    reg      0.1691004469  1.132230e-02   14.9351735  5.082589e-50 
    ...

However, it returns Error: $ operator is invalid for atomic vectors, even if I did not use $ operator here.

(2) Also, I want to create a column 'year' containing repeated values of the associated year and am trying to loop over this:

premium1999$year <- 1999

In which I wrote:

for (i in seq(1999,2008)) {
    assign(paste0('premium',i)[['year']], i) 
}

In this case, it returns Error in paste0("premium", i)[["year"]]: subscript out of bounds

(3) Moreover, I'd like to repeat some rows and loop over:

premium1999 <- rbind(premium1999, premium1999[rep(1, 2),])

for 10 years again and I wrote:

for (year in seq(1999,2008)) {
    paste0('premium',year) <- rbind(paste0('premium',year), paste0('premium',year)[rep(1, 2),])
}

This time it returns Error in paste0("premium", year)[rep(1, 2), ]: incorrect number of dimensions

I also tried to loop over a few other similar things but I always get Error.

Each code works fine individually.

I could not find what I did wrong. Any help or suggestions would be very highly appreciated.

For your issue 1, try this: for (year in seq(1999,2008)) { assign (paste0('premium',year), <whatever_value_you need>) } It seems to me you are using unnecessary loops. If you specify sample data input and expected output (no screen shots please), it will be easier to help. — Shan R
– Shan R, Commented May 14, 2020 at 16:37
I tried but it still returns the same error. I will edit more info about concerning (1) problem on the thread. I want to extract the regression estimators from the "data1999_mod" for rows 19 to 44 as a data frame. — Variya
– Variya, Commented May 14, 2020 at 16:47

Mohanasundaram · Accepted Answer · 2020-05-14 20:07:27Z

1

The problem with the code is that the paste0() function returns the character and not calling the object that is having the name as this character. For example, paste0('data',year,'_mod') returns a character vector of length 1, i.e., "data1999_mod" and not calling the object data1999_mod.

For easy understanding, there is huge a difference between, "data1999_mod"["Estimate"] and data1999_mod["Estimate"]. Subsetting as data frame merely by paste0() function returns the former, however, the expected output will be given by the latter only. That is why you are getting, Error: $ operator is invalid for atomic vectors.

The same error is found in all of your codes. On order to call the object by the output of a paste0() function, we need to enclose is by get().

As, you have not supplied the reproducible sample, I couldn't test it. However, you can try running these.

#(1)

for (year in seq(1999,2008)) { 
  paste0('premium',year) <- as.data.frame(coef(summary(get(paste0('data',year,'_mod'))))[c(19:44), 1])
}


#(2)

for (i in seq(1999,2008)) {
  assign(get(paste0('premium',i))[['year']], i) 
}


#(3)

for (year in seq(1999,2008)) {
  paste0('premium',year) <- rbind(get(paste0('premium',year)), get(paste0('premium',year))[rep(1, 2),])
}

answered May 14, 2020 at 20:07

Mohanasundaram

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3 Comments

Variya Over a year ago

Thank you very much. I tried the code you gave me but the first and third one still returns error <target of assignment expands to non-language object> and the second one returns Error <invalid first argument>. I actually tried using get() before too, but none of it worked..

Mohanasundaram Over a year ago

Can you update a minimal reproducible sample, so that I could run the code and edit my answer?

Variya Over a year ago

Hi. thank you very much. I think I know what the problem was. The code get() works after all. However, the left side still also returns "premium1999" because of paste0(). So I have created a list to store each dataframe so that it can be called by, for example, premium[["premium1999"]] instead. By doing this, I can use paste0() inside the parentheses, and it works. Thank you very much for your explanation about the paste0() code.

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