I have a data table, `A` like:

```
year          location    sigma_NN_1 sigma_NN_2 sigma_NN_3
2076 43.59375_-116.78125  1.4681173   1.664289   1.735974
2077 43.59375_-116.78125  1.3798515   1.550524   1.551269
2078 43.59375_-116.78125  0.7934367   1.064248   1.177981
2079 43.59375_-116.78125  1.8235574   1.991018   2.288402
2080 43.59375_-116.78125  2.5560329   2.578093   2.589334

```

And I want to use it to mask another data table where the value of sigmas are below a threshold, lets say 2. Lets say my second data table is `B`

```
year            location       location_NN_1      location_NN_2      location_NN_3
2076 43.59375_-116.78125  41.15625_-90.65625 41.21875_-90.65625 41.15625_-90.65625
2077 43.59375_-116.78125  43.34375_-78.15625 43.34375_-78.21875 43.28125_-78.15625
2078 43.59375_-116.78125  41.34375_-90.78125 41.21875_-90.65625 41.53125_-73.96875
2079 43.59375_-116.78125 43.53125_-116.78125 41.34375_-90.78125 41.71875_-74.15625
2080 43.59375_-116.78125  41.34375_-90.78125 41.96875_-86.21875 41.21875_-90.65625

```

So, I want to have something like `B[A<2]`, but obviously this does not work, otherwise, I would not be here.

Any suggestions?

Expected output:

output

```
year            location       location_NN_1      location_NN_2      location_NN_3
2076 43.59375_-116.78125  41.15625_-90.65625 41.21875_-90.65625 41.15625_-90.65625
2077 43.59375_-116.78125  43.34375_-78.15625 43.34375_-78.21875 43.28125_-78.15625
2078 43.59375_-116.78125  41.34375_-90.78125 41.21875_-90.65625 41.53125_-73.96875
2079 43.59375_-116.78125 43.53125_-116.78125 41.34375_-90.78125                 NA
2080 43.59375_-116.78125                  NA                 NA                 NA

```

The goal is to find locations whose corresponding sigma in data table `A` is less than 2.