Understanding the Error: Unexpected Token ‘*’ and ‘-’

In this post, we’ll delve into the unexpected error message “Unexpected token”*" and “-”. This issue is commonly encountered in R programming, particularly when working with time series data. We’ll explore the underlying causes of this error, discuss its implications, and provide a step-by-step solution to resolve it.

Introduction to Time Series Data

Time series data is a sequence of numerical values measured at regular time intervals. It’s widely used in finance, economics, and other fields to analyze trends, patterns, and correlations over time. In R, time series data can be created using the timeSeries() function, which allows for various operations such as aggregation, filtering, and plotting.

The Role of Names() Function

The names() function returns the names of the elements in a vector or list. When used with time series data, it’s essential to provide a character vector that matches the number of observations. This ensures correct alignment of the time series data during operations like aggregation or filtering.

In the provided code snippet:

GMVPort = timeSeries(cumprod(GMVRetFac), charvec = names(GMVRetFac))
CVARPort = timeSeries(cumprod(CVARRetFac), charvec = names(CVARRetFac))

The names() function is used to provide a character vector that corresponds to the number of observations in the GMVRetFac and CVARRetFac variables. However, this approach can lead to errors if the length of the names() output does not match the expected number of observations.

The Error: Unexpected Token ‘*’

The error “Unexpected token*”" occurs when R encounters a character vector containing an unexpected symbol (*). This issue arises from the fact that the charvec argument in the timeSeries() function is case-sensitive, and it expects a specific format for the character vector.

In the provided code snippet:

GMVPort = timeSeries(cumprod(GMVRetFac), charvec = names(GMVRetFac))
CVARPort = timeSeries(cumprod(CVARRetFac), charvec = names(CVARRetFac))

## Relative performance

RelOutPerf = ((CVARPort - GMVPort) / GMVPort) * 100

The charvec argument is passed a vector containing the element-wise product of two time series. However, R interprets names(GMVRetFac) as a character vector with unexpected symbols (*) and -. As a result, it throws an error.

Resolving the Error

To resolve this issue, you need to modify the charvec argument to ensure it matches the expected format for the time series data. Here’s a revised version of the code snippet:

GMVPort = timeSeries(cumprod(GMVRetFac))
CVARPort = timeSeries(cumprod(CVARRetFac))

## Plotting of portfolio values

ylims = range(cbind(GMVPort, CVARPort))

plot(GMVPort, ylim = ylims, xlab = "", ylab = "Portfolio Value (Index)")

lines(CVARPort, col = "blue")

legend("topleft", legend = c("Minimum-Variance", "Minimum-CVaR"), col = c("black", "blue"), lty = 1)

## Relative performance

RelOutPerf = ((CVARPort - GMVPort) / GMVPort) * 100

In this revised version, we’ve removed the charvec argument from both the timeSeries() functions. This allows R to correctly interpret the data and avoid unexpected token errors.

Best Practices for Working with Time Series Data

Here are some best practices to keep in mind when working with time series data:

• Always verify that the length of the character vector passed to the charvec argument matches the expected number of observations.
• Use meaningful variable names and follow standard conventions to avoid confusion and errors.
• Ensure that all calculations involving time series data are performed correctly, using correct operator precedence and grouping rules.

Conclusion

The unexpected token error “*”" is a common issue encountered when working with time series data in R. By understanding the underlying causes of this error and following best practices for working with time series data, you can resolve issues like this and improve your overall coding efficiency and accuracy.

Last modified on 2024-06-11