get shortcode value

    add_shortcode('the_chart ', 'high_chart');
        function high_chart($atts, $content = null) {
           //extract the cart and footer_caption value 
            extract(shortcode_atts(array( 'chart' => null, 'footer_caption' => null), $atts));
            /*
               * process your chart and footer_caption value as
               * $chart and $footer_caption and return the process data
             */
            $return_html="chart id:". $chart.'<br/> Footer Caption:'. 
            $footer_caption;
            return $return_html

        }

For reference: https://codex.wordpress.org/Function_Reference/add_shortcode
Hope that you understand!