Increase size of one of the series in R highchart - r

Question

I'm trying to show a line and % changes in a single highchart plot, but the changes are very little and It can't be seen in the plot. I made a simplified code to show my problem:
a <- c(300,200, 400, 10, 40, 80)
b <- c(0.8, 2, -2, -1.5, -1.1, 2)
d<-cbind(a,b)
dt <- seq(as.Date("2018-01-01"), as.Date("2018-01-06"), by = "days")
ts <- xts(d, dt )
highchart(type="stock") %>%
hc_add_series(ts$a,
type = "line",
color="black") %>%
hc_add_series(ts$b,
type = "lollipop",
color="red")
I need to increase the size of "ts$b" in the plot, how can I do it? I also tried with two axis, but It seems doesn't solve the problem.

Answer 1

I see two solutions to achieve that.
The first you mentioned - using two yAxis and manipulating their height and top distance.
Example JS code:
yAxis: [{
height: '90%',
opposite: false
},
{
visible: false,
top: '83%',
height: '15%',
}
]
Demo:
https://jsfiddle.net/BlackLabel/0826r7sh/
Another way is using a modified logarithmic axis. Negative values can't be plotted on a log axis, because by nature, the axis will only show positive values. In that case you need to use a custom extension according to the following thread:
Highcharts negative logarithmic scale solution stopped working
(function(H) {
H.addEvent(H.Axis, 'afterInit', function() {
const logarithmic = this.logarithmic;
if (logarithmic && this.options.custom.allowNegativeLog) {
// Avoid errors on negative numbers on a log axis
this.positiveValuesOnly = false;
// Override the converter functions
logarithmic.log2lin = num => {
const isNegative = num < 0;
let adjustedNum = Math.abs(num);
if (adjustedNum < 10) {
adjustedNum += (10 - adjustedNum) / 10;
}
const result = Math.log(adjustedNum) / Math.LN10;
return isNegative ? -result : result;
};
logarithmic.lin2log = num => {
const isNegative = num < 0;
let result = Math.pow(10, Math.abs(num));
if (result < 10) {
result = (10 * (result - 1)) / (10 - 1);
}
return isNegative ? -result : result;
};
}
});
}(Highcharts));
.
yAxis: {
type: 'logarithmic',
custom: {
allowNegativeLog: true
}
},
Demo
https://jsfiddle.net/BlackLabel/nw6osucm/