google areachart cannot access datatable rows -

i'm using google chart api draw area chart. chart represents altimetric profile , when pass mouse on it, shows position (lat , long) underlying data table.

so created chart:

data = new google.visualization.datatable(json); chart = new google.visualization.areachart(document.getelementbyid("chart-output")); 

and draw it:

chart.draw(data, options); 

and add handler mouseover event

when event triggers, want row underlying data source

if (event.row != null && event.column != null){    //data chart datasource   var o = data.d[event.row];   var sel_x = o.c[0]["coords"]["x"];   var sel_y = o.c[0]["coords"]["y"];    ...  //show x, y } 

the point when project first released, last year, worked fine , property data.d contained desired value. now, i've found same property undefined , rows array found in property data.tf.

i expect gain access datasource rows through getter method, cannot find right one. datatable method ǵetrowproperties(rowindex) not provide content.

what doing wrong?

thanks , regards

**edit 12/09 **

@juvian yr reply, it's bit more complicated that. datasource this:

   {"cols":     [      {"id":"distance","label":"distance","type":"number"},      {"id":"asfaltocemento","label":"asphalt/beton","type":"number"},      {"id":"rocciaghiaia","label":"fels/schotter","type":"number"},      {"id":"ghiaccio","label":"eis","type":"number"},      {"id":"terraprato","label":"erde/wiese","type":"number"},      {"id":"sassolastricato","label":"stein/pflaster","type":"number"},      {"id":"sconosciuto","label":"unbekannt","type":"number"}],     "rows":     [      {"c":[{"v":0,"coords":          {"x":1296400.1245177952,"y":5885847.104437432,"z":1345.275458520788,"segment_no":0}},{},{"v":1345.275458520788},{},{},{},{}]},      {"c":[{"v":2.8740587294156668,"coords":{"x":1296395.9416741736,"y":5885847.412533606,"z":1345.4754191288682,"segment_no":0}},{},{"v":1345.4754191288682},{},{},{},{}]},      {"c":[{"v":17.583008965075226,"coords":{"x":1296374.532888888,"y":5885848.966197753,"z":1346.3169989102385,"segment_no":0}},{},{"v":1346.3169989102385},{},{},{},{}]},      {"c":[{"v":23.830815143830804,"coords":{"x":1296365.4205057025,"y":5885849.273363226,"z":1346.724445260275,"segment_no":0}}, {},{"v":1346.724445260275},{},{},{},{}]},       ....    ]} 

when event graphic, retrieve needed values way:

var o = data.tf[event.row]; var sel_x = o.c[0]["coords"]["x"]; var sel_y = o.c[0]["coords"]["y"]; 

i know it's not practise use property (tf) , should use accessor getvalue(), using getvalue method can't access 'coords' object , subobject.

any appreciated

well, data.d not public method, google can make changes that, should use public methods instead consistency.

try this:

var sel_x = data.getvalue(event.row, 0); // supposing x value in fisrt column var sel_y = data.getvalue(event.row, 1); // supposing y value in second column 

more info here: google datatable