I have a data frame with 70variables, I want to create a new variable which counts the number of occurrences where the 70 variables take the value "mq" on a per row basis.

I am looking for something like this:

```
[ID] [Var1] [Var2] [Count_mq]
1.    mq    mq      2
2.    1     mq      1
3.    1      7      0

```

I have found this solution: 

count\_row\_if("mq",DT) 

But it gives me a vector with those values for the whole data frame and it is quite slow to compute. 

I would like to find a solution using the function apply() but I don't know how to achieve this.

Best.