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I am fitting a time series model in R. I plotted the time series to check for the pattern of it. It has 30625 observations. The observations are half hourly

`plot.ts(ts)`

I was checking **acf** plot to see for auto correlation.

`acf(ts)`

If ACF plot decreases slowly i.e. it has auto correlation out to higher number of lags, then it probably needs higher order of differencing.

I took the logarithm of the series and then checked its acf plot.

`acf(log(ts))`

I am getting an error

```
Error in plot.window(...) : need finite 'ylim' values
In addition: Warning messages:
1: In min(x) : no non-missing arguments to min; returning Inf
2: In max(x) : no non-missing arguments to max; returning -Inf
```

What does this error means? What should I do remove this error. I also think the significance bounds given by dotted line are not correctly calculated. What should I do in these two cases?

1Better to apply transformations like $\log(x + 1)$ or $\log(|x| + 1)$ depending on you data! – Ehsan M. Kermani – 2017-04-13T16:49:38.933