80-example-05.Rmd

# Donors who aren't degreeholders {#ex-sim-donors}

```{r ex-sim-donors-loadlib, message = FALSE}
# i always begin by loading the disco engine if it isn't already loaded
library(discoveryengine)
```

We have what looks like an easy request:

> Find donors to the School of Information who are not SIM degree holders.

Having already looked up the codes, you immediately think: 

```{r eval = FALSE}
gave_to_area(SIM) %but_not% has_degree_from(LI)
```

Unfortunately, as you begin reviewing the results, you notice that you produced a list that includes spouses of degree holders who received credit for household gifts to SIM. 

To get around the issue, use the `married_to` widget (a [higher-order widget](#higher-order-widgets)). Note the use of parentheses to ensure the correct interpretation:

```{r}
alum = has_degree_from(LI)
non_alum_donor = 
    gave_to_area(SIM) %but_not%
    (alum %or% married_to(alum))
```