I would like to plot two time-series on a same graph. One series takes much larger values than the other, so I thought a semilog scale might be appropriate (i.e. linear X (dates) and log Y). However, both series take on negative and positive values. Does it still make sense to use a log scale? If so, should I transform both series as follows?
if observation > 0 log_observation = log(observation) elseif observation < 0 log_observation = -log(-observation) else log_observation = 0