Hello venkatesh!
Thanks for contacting us with your question!
Logarithms of negative numbers are not defined in the real numbers. The natural logarithm function ln(x) is defined only for x>0. So the natural logarithm of a negative number is undefined. But there is a little trick in Highcharts, you can use some custom options and use custom plugin to wrap some core functions to achieve working negative values in logarithmic type. You can check it in the demo below.
Demo: https://jsfiddle.net/gh/get/library/pur ... -negative/
Let me know if you have any further questions.
Regards!