there are several wrong things in your code:

1. you shouldn't write your script in an import script (line 1)
2. you should use es6's let and const instead of var
3. in your checks (lines 9, 11 and 13) you should have at least a double equal sign == to compare, one equal sign is used to assign values.

Fixing these little things you should end up with something like this:

<div class="row" style="margin:auto; padding: 8px 8px 0" id="categories">
<button id="eqty" class="btn btn-primary" style='margin: 0 8px' onclick="clicked()">Equity Chart</button>
<button id="debt" class="btn btn-primary" style='margin: 0 8px' onclick="clicked()">Debt Chart</button>
<button id="hyb" class="btn btn-primary" style='margin: 0 8px' onclick="clicked()">Hybrid Chart</button>
</div>

<script src="https://cdnjs.cloudflare.com/ajax/libs/jquery/3.3.1/jquery.min.js"></script>
<script>
    let chartdata = [];
    const eqdata = [['a',2],['b',6],['r',9],['s',8]];
    const debdata =  [['p',2],['r',6],['r',9],['d',8]];
    const hybdata =  [['l',2],['k',6],['rr',9],['df',8]];
    
    function clicked(){
        const id = event.srcElement.id
        if (id == 'eqty'){
            chartdata = eqdata;
        } else if (id == "debt"){
            chartdata = debdata;
        } else if (id == "hyb"){
            chartdata = hybdata;
        }
    };
</script>