Image Formula Field Isn't Working

Question

I would like an image to show based on the "Rating" field picklist value. I keep getting syntax errors. Here's what I have.

IMAGE( IF(ISPICKVAL(Rating, "Cold"),"/servlet/servlet.FileDownload?file=015J0000000Wb4Q", IF(ISPICKVAL(Rating, "Warm"), "/servlet/servlet.FileDownload?file=015J0000000Wb4d", IF(ISPICKVAL(Rating, "Hot"), "/servlet/servlet.FileDownload?file=015J0000000Wb4b"), ) ) )

Answer 1

A simpler way to write this would be to use the CASE function vs. the IF statements, so something like this:

IMAGE(Case(Rating, 
    "Cold","/servlet/servlet.FileDownload?file=015J0000000Wb4Q", 
    "Warm", "/servlet/servlet.FileDownload?file=015J0000000Wb4d", 
    "Hot", "/servlet/servlet.FileDownload?file=015J0000000Wb4b",
    ""),
"rating")

Similar to the example below from the help docs here.

IMAGE( 
CASE( Priority, 
"Low", "/img/samples/flag_green.gif",
"Medium", "/img/samples/flag_yellow.gif",
"High", "/img/samples/flag_red.gif", 
"/s.gif"), 
"Priority Flag")

Answer 2

You left off the final ELSE argument on the third IF() function - I reworked the formula to be easier to read, assuming the "Cold" is the default image:

IF(ISPICKVAL(Rating, "Hot"), IMAGE("/servlet/servlet.FileDownload?file=015J0000000Wb4b"), 
  IF (ISPICKVAL(Rating, "Warm", IMAGE("/servlet/servlet.FileDownload?file=015J0000000Wb4d"), 
    IF (ISPICKVAL(Rating, "Cold", IMAGE("/servlet/servlet.FileDownload?file=015J0000000Wb4Q"), 
      IMAGE("/servlet/servlet.FileDownload?file=015J0000000Wb4Q")
    )
  )
)

Answer 3

Here is the Example which i have used related for "TrafficSignals".Traffic signal is a picklist field with Red,yellow and Green.

IF :IF(logical_test, value_if_true, value_if_false)

Image :IMAGE(image_url, alternate_text [, height, width])

IF( ISPICKVAL(TrafficSignals__c, "Red"), 
    IMAGE("/img/samples/light_red.gif", "red",32,32), 
IF( ISPICKVAL(TrafficSignals__c, "Yellow"),
    IMAGE("/img/samples/light_yellow.gif", "yellow",32,32),
    IMAGE("/img/samples/light_green.gif", "green",32,32) 
) 
)