How can I concatenate strings and use them as a list name?

Question

I have these lists: models_results_ZL, models_results_B2 and models_results_B4 that contain numbers.

For example:

> models_results_ZL
[1] 245.1907896  29.9200000   0.9000181  34.0000000
> models_results_B2
[1] 264.9851283  53.7100000   0.9163977  32.0000000
> models_results_B4
[1] 289.7529856  52.5600000   0.9229745  31.0000000

I have the list both_constr_satisfied that contains "B2","B4". This list is not static. It may contains different combinations of "ZL", "B2" and "B4". For example:

> both_constr_satisfied
[1] "B2" "B4"

Regarding the values of both_constr_satisfied I want to get the first value of the corresponding models_results lists. e.g. For this example I want to get models_results_B2[1] and models_results_B4[1] and store them to a new list. e.g. new_list = [264.9851283, 289.7529856]

How can I concatenate strings and use them as a list name?

I'm trying the following code, but var_name is just a string not a list.

VQ_options=c()
for (option in length(both_constr_satisfied)){
    assign(var_name, paste0("models_results_",both_constr_satisfied[option+1]))
    VQ_options = var_name[1]
  }

Can you please add reproducible example of both model_results and both_constr_satisfied lists — Sotos
– Sotos, Commented May 8, 2017 at 9:07
@Sotos There is no list named model_results. There are 3 different lists that have the same initial name. model_results_ZL, model_results_B2 and model_results_B4. I want to concatenate model_results with the values of both_constr_satisfied and use these as lists. I added examples of these. I will add also for both_constr_satisfied. — zinon
– zinon, Commented May 8, 2017 at 9:10

Roman · Accepted Answer · 2017-05-08 09:34:30Z

1

You can try:

# Some data 
a <- list(models_results_ZL=1:10, models_results_B2=10:1, models_results_B4=11:20)
a
$models_results_ZL
[1]  1  2  3  4  5  6  7  8  9 10

$models_results_B2
[1] 10  9  8  7  6  5  4  3  2  1

$models_results_B4
[1] 11 12 13 14 15 16 17 18 19 20

both_constr_satisfied <- list(c("B2", "B4"))

# change names according the both_constr_satisfied list
a <- setNames(a, unlist(lapply(strsplit(names(a), "_"), "[", 3)))
names(a)
[1] "ZL" "B2" "B4"

# extract the first value, respectively
lapply(a[unlist(both_constr_satisfied)], "[", 1)
$B2
[1] 10

$B4
[1] 11

answered May 8, 2017 at 9:34

Roman

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1 Comment

zinon Over a year ago

Great! Thank you!!

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